NO...neither is near as heavy duty as a 350 old diesel. they might be "made" that way,but still will never hold up. a well maintained 350 old diesel is a ok engine,and will run many miles,but many owners drove them a gassers,and they died./6 has no good points for a diesel conversion...maybe a 383?,w/ tons of mods...look at how much more btu's diesel is than gasoline,and transfer that into power,and stress...not good!..ever look at a 7.3 ford,or a cummings??? there is a reason why they weigh a ton! BEEF! and as far as E85,whats the point of this? fuel mileage? power? alky uses much more fuel than gas for same btu's,let alone diesel. so if mileage is the reason...forget it. and as for power,well....use nitro...lol.