Well as mentioned the sonic map is the best way to confirm overall thickness. Be sure the shop is competent as some can't use sonic equipment to save their lives. I've been witness to that one. But in the meantime there is a easy field test you can do to check the blocks cyl wall cores. You can remove the blocks freeze plugs and see what size drill bit shank fits between the cyl wall cores. This will tell you what's in there. Natch coreshift can be a concern. Use a 13/64" and 15/64" drill bits. See if the 13/64" is a snug fit in the gap. If so and coreshift permitting you can possibly get a 428 4.13+ bore out of it. If the 15/64" bit is a tight fit it has std 390 wall cores and at best a .060 4.11 bore is possible with minimal coreshift. This test will at least let you know right away what wallcores the block has. You can then look at the cranksaddle area and look for the HD "crows feet" crank webbing and beefy crank saddle area. FT castings were all HD so I'm sure it's all HD inside. It's has been found some of the FT castings have crossbolt bosses. This can make it easier to crossbolt the maincaps if desired. But not always needed. Just another neat trait some of the blocks have. Everything else the guys have told you is spot on.


G.