700r4 opinions?

[frankenstein]

I'm getting ready to build a truck it has a grenaded th400 and a 206, but I have a 700r4 and a 208 the 700r4 as of now blew the pan gasket so its toasted, but id liek to have overdrive, its goin in a 73 k20 with a 350hpish long rod 400, with a gm14 bolt rear, and D44 front, with 4.56's, ive herd alot off goods and bads about it, ive been told to change the front planetary with a newer model one? any truth to that ro does it matter?