Just another added piece of info...
the rear of that car is a 10bolt 8.5"
you can go with a set of 3.42's to make it a bit snappy and still be able to hit the highway.
the standard rear as is will hold to my previous post.
What is the tire size you are planning to run?
As for the overdrive trans...Just remember to put in that 12volt switch to turn off the overdrive.
this is allows you to stomp on the gas and go, turn the switch back and you can cruise at desired speed.
Remember going with a 200-or-700 you have to change the driveshaft length.
Have the th350 built with good hard parts and it can hold a solid 500hp.
I have a th350 with LENCO internals and a hughes 2500stall converter.  I spent 1800 on the package. *i may have an advantage, LENCO is 9 blocks from me*  

Bracketry for the front accessory drive on a Big Block Chevy is available NEW just about anywhere and the 350 trans has the same bolt pattern. The distributor and ignition even interchanges. Headers are abundant for that chassis/engine combination.
Get a 454 Chevy from a 90's truck and go onward from there; there is NO substitute for cubic inches.