Would a Marciano born in the 80s or 90s have been trained as a HW?

No. Even though that was his biggest. But guys do not usually compete in a division when they are lower in the range of weight allowed, especially when it is such a big range like CW.
I am saying that since even his stated peak of 187/188 was more than his career average, he is more likely to weight cut.
This is how he would likely be advised...

Although it would not be so unlikely they could bulk him up to the CW max-but more likely when it was 190.
Because of his relatively small frame & to keep his endurance & not sacrifice speed.

 

Sorry the idea that weight training is bad for sports is just completely wrong.
It is a really antediluvian idea that has been disproved forever.
Weight training is used in most all sports; if you are right all the athletes that are so dominant & setting world records somehow would do even better without it-the opposite is in evidence.

The idea that blood only goes in certain places is not scientifically valid.
That does not mean this is mutually exclusive with sports-specific training-of course most of the stuff you cite is very useful!
That numerous men & woman benefit from sports specific weight training does not mean that say skipping rope or swinging a bat or practicing shooting/rebounds/positioning is not crucial!

Even naturally very strong athletes benefit from lifting.
Done right it gives you ore energy & muscular endurance too.
Lawrence Taylor could have been even better longer with it.
Michael Jordan like innumerable athletes bulked up to handle the rigors of physical play & holding his ground.
Charles Barkley was innately much stronger but regretted not lifting.
And those who train harder & well-but not overtrain-tend to be good or great longer....
Like Karl Malone, not quite as good as "Sir Charles/The Round Mound of Rebound" at their very peak, but better over many years.

Even a sport like sprinting (they discovered decades ago) maximizes ability when guys & gals are stronger & more explosive-although less mass than many other sports.
The thin sprinter from the 1970's & before was generally not getting as much out of their body.
"Bullet" Bob Hayes was modern sized & better than any thin sprinter ever, & most all ever compensating for conditions such as track, shoes, starting blocks...

The whole science of cross-training is exceedingly well established.

 

He actually fought at 184 vs Walcott and 187 vs Charles ... a cruiserweight for sure today ..

 

I think that with the lower limit of the heavyweight division at 190, the money at heavyweight might look very tempting, especially in the eras when teh cruiserweight division was a wasteland.

If you look at the top cruisers of the 80s, most of them ended up at heavyweight, even if they weren't necessarily very successful.

Once the heavyweight division moves to 200 it becomes more of a leap, though still not impossible.

 

Specialized weight training has benefits for some sports. Arm wrestling for example sometimes an athlete might not always have strong arms to work out with they can supplement weight training in.

Boxing you are better off just training boxing. It’s weight training in a sense it’s just moving the weight of the glove with punches. Or moving the weight of the body around with their legs in a sense sparing and bag work and mit work are weight training, the right kind.kettle bell swing, Benching , squating and dead lift you don’t need for boxing, wrong muscles.

 

With today's training and eating and yes roids, I can see that 185 pound body getting bigger and Marciano would enter the ring around maybe 264 or so pounds. He be larger and stronger and he will hit harder as well.

 

Possibly yes but I don’t know if it would have been in his best interest unless he was matched VERY selectively and carefully

 

He was too short to be a heavy in the 80`s, he would have been the right height for super middle in the 90`s.

 

5`9! AJ isn`t harder to hit than Larry Holmes and he just passed his latest Vada test.

 

So what weight could Marciano bulk up to, without becoming over muscled?

Personally I think about 205lbs.

More than that and it is going to be counterproductive.

That is almost exactly what Eddie Chambers weighed when he challenged for the title, so I woudl not say that it is impossible, even when the division starts at 200.

Whether it would be advisable, is another question entirely.

Personally all my instincts as his manager, woudl be saying that I had a small cruiserweight.

Now in the early 80s I don't see it as being nearly as much of an issue.

 

Those are the weights of today's LHWs.

 

And probably some of the smaller cruiserweights, if they were really in shape.

When Moore fought Marciano for he title, Moore actually outweighed Marciano, and he was the current Light Heavyweight Champion.

 

That just proves bulking up does not work against Marciano.

 

For the record the biggest light heavies, have always come in somewhere in the mid to high 180s, in heavyweight fights and catchweight fights.

Always.

Of course I don't know what they weighed in the ring, when they fought at light heavy, because that information did not survive.

 

Which CVs would that be?

Not any of the ones I know at least - like Haye, Hunter, Cunningham, Usyk, Gassiev, Briedis and Okolie. Bellew was a LHW, but he looked to have put on mostly solid mass as a CW. Not ripped, but not out of shape either.

Draining to make 200 is certainly the norm among the top CVs today. Marciano would, at the size he was, be giving up at least 20-25 lbs against them, while being of pretty average size for top LHWs.