Same deal on the older ones. Now if you go really old as in 67-72 I found they had a lot thicker castings but due to the age of them you should still check them out, the thick places may have rustred into thin places due to years of neglect. Another option is the poly 318 blocks, they were very thick and LA heads bolt right on but again they are all very old now. It sounds like you are wanting one for the easy use of a roller cam, in that case you are just gonna have to sonic test to be sure you can go any bigger. Luckily the roller and magnum blocks tend to have much less core shift than the older blocks eve though they tend to be thinner on average, just not as much varriation between the best and worse.
