Is a gen. iv 454 block the same as a LS6 454 block??

1970, ls6 ?

My 1989 365mag was the same looking block as my 70 Chevelle,Ran it for years at 765 hp in my Scarab.

Only if it's a four bolt main. It also might be possible that the LS6 was a high nickel block as well.

Yes it's a 4 bolt main.

I dont think the 70's they had a diffearnce in nickel,I know I bought a nascar chevy bowtie cnc block in 99 and it looked like a shinny nickle, I also bought a ford motorsport block for my mustang that year and it was a dull cast color, but it was about the same weight

why ya wana know?

+1 yep back then the blocks has way more nickel in them for strength.. the newer mark blocks machine easier,,the older ones seem to be harder and take longer to machine the deck.