I am intrested in building a 6.5. Ive been reading around, and bill heaths salt flat truck, engine had the 6.2l block, is the 6.2l block stronger than the 6.5 block.
The salt flat truck also used the 6.2l pistons, so would it basickly be wise to use a 6.2 bottom end and use a 6.5l top end, i would plan on installing this in my daily driver, and i dont pull a heavy trailer often but when i do pull a trailer it is usually heavy.
Strongest block is the new Optimizer made by GEP that has the crack problems designed out of it. Some love their trucks enough to spend the cash for this.
A 6.5 is simply a bored out 6.2 with thinner ceramic coated pistons. I have cracked the mains in both 6.2's and 6.5's as have many others.
I am cheap and have been using low mile, less than 30K, military surplus 6.2 engines. After 30K more miles of hard towing with the power turned up I found cracks in the mains when I tore the engine down after eating a 1/4 worm clamp dropped in the intake during an IP change. The engine is still running with the cracks but has a numbered day of failure in the future... I figure it can go around another 100K and am curious when it will blow up.