Matt, you are technically correct the 350 Diesel Is not a converted Gas engine. . it is a completely different block. . It isn't a gas engine with different heads or a gas engine sleeved, etc etc. . There was no gas Oldsmobile engine sharing the same block, but it was based on the 350 Olds Rocket motor. The Diesel block is specific to the diesel; it is a heftier, more solid block with stronger mains and a port in the valley for the injection pump adapter. The block is cast with high nickel content. The 350 Diesel is not a converted gas block but can however be converted into a gas engine. The crank of the 350 diesel which uses 455-type mains with standard small-block rod journals is not interchangeable with the gasser but it will take the 350 gas pistons and rods (can’t use the diesel rods they are slightly shorter). The diesel blocks are preferred for all-out racing because of their 3/8-inch thick main webs and . 400-inch-thick cylinder walls. A 425 crank with cut-down counterweights will fit in the diesel block. Since, with sonic testing, the diesel block will accept a 4. 25-inch bore, up to 451 inches is available with custom pistons and rods (what a sleeper!) 455 cranks won't clear no matter what you do).