Mine too, lots of unbelievable talent passed threw here. And there's plenty of HWs who were LHW sized as well. http://boxrec.com/media/index.php/Division-By-Division_-_The_Greatest_Fighters_of_All-Time What do you think of rings list? Here's mine https://www.boxingforum24.com/threads/top-10-light-heavyweights.626500/
This is how I see it. Foster might be one of the more overrated ATG's out there. Painfully thin resume.
Spinks is the much greater of the two, but head-to-head I'm going with Foster. I think Bob had the tools to be a nightmare for Spinks, and the firepower to take him out. Foster KO 10
I like your list, though I always ranked Fitz as a LHW after he won MW title. Even though the division didn't exist back then, he fought many greats within that weight limit. Langford is tougher as he fought a lot over 175.
At this time, I feel Michael would pull off a close decision, like 8-7 or 9-6. But he would have to be on his P's and Q's from jump, and nullify Foster, which he would do with great difficulty.