Yes also they were 5"10 and would campaign at Cruiserweight today. What's their chance vs. modern day SHWs even if they're as horribel as Wilder? Slim to none. Few today would pick Kovalev vs. Wilder. However, seemingly everyone would pick Frazier over Wilder. It's a type of nostalgica bias.
While I have yet to see a heavyweight with the overall package that say a Ali had or the technical beauty joe Louis displayed or the rugged power and tenacity of Marciano I'd have to give a slight edge to today's champs simply because of evolution, natural ability and tons of other intangibles surrounding health nutrition strength training and condition et etc.... Kova landing an awesomely timed pinch can certainly rock wilders world but it's far fetched and one nice hook or right hand would change kovo's approach completely....styles make fights and I'd pick Eddie chambers to dominate and stop kovo and he's a fringe contender.
CW is kinda pushing it actually, CWs are mostly 6'2, 6'3 guys. 5'10 180lb guys are like SMW/LHW level.
Kovalev could do it given his skill, power and Wilder's dodgy jaw. I wouldn't bet on it though. Big size difference.