Th350 to 700R? or Th400? HELP!

[Charles90706]

So in the the 3 months I have owned my 86 GMC shortbed I have done some major work with the most recent being the flip kit in the rear and 6inchs off the front.

Two days ago the transmission completely failed. it started slipping and finally didnt engage the gear at all... I added 3 quarts of fresh fluid and made it home to where it is resting in my back yard.

It is currently equipped with a TH350 (which SUCKS because it doesnt have overdrive)

I WAS A TRANSMISSION WITH OVERDRIVE!!!

I have had corvettes and each can with a 700R that shifted great both before and after being rebuilt.

I know the 700R is a option but I am not sure what kinda of price range for supporting parts (torque converter, flex plate, starter, crossmember, tranny mount, drive shaft, etc) it will need new and which ones I will be able to re-use

Is there another option perhaps a TH400? if so what will i need with that?

Main goal is to make this truck more highway friendly, The most it will be towing is a car dolly in southern california...

Thanks in advance for all your help!~