Use legalpad cardboard, layered to thickness, to testfit a 4" or 3.79" 318/390 crank in a larger 360 block mains. With stock pistons.

[Jessearent]

Use legalpad cardboard, strips cut, layered to tichkness to test fit a 3.79"/4" 318/390 crank in a 360 block...with stock pistons.

 

[rumblefish360]

Interesting statement. No question?

Something I’d surely not do. I’d use the intended gasket or no gasket and clay to measure the distance/clearance. Though I’m sure the stock pistons would pop out way to much.