the th700r4 is very popular casue it works well in cars without computers. Also has low first and taller top gear. It helps alot. But it is heavier and uses more hp to turn it over. Or parastatic drag? i think its called. Not that i can spell worth a crap. and i love the powerglide but for any street car the th700r4 will make you very happy. Also with gas prices these days and trans being for sale around 1000 bucks the 700r4 will pay for its self over time. That in its self is very rare in the fast car world.
Do you have 4 valve relief pistons they may have as much as 6 cc depth and still be flat tops. if rebuilder pistons it may be even more. You did .041 as gasket height?
Normal deck is .025 and .010 is normal after being cut.
hope this helps.