Retro fit TH400 instead of 4l80E

[tators]

I'm looking at buying a tow rig...(one thats paid for)

91' 3/4 Chevy, 350 TBI, it came with a 4l80e but it has been removed... It is being sold with a loose 700r4

I'm not looking to spend alot of money....

Should I - 1) buy a junkyard 4l80e ? (seem to be $500-$1000 range)

2) put in the 700r4 and hope for the best....

3) put in a rebuilt TH400 ?

I don't plan on doing any un-loaded highway cruising.... so do I need an overdrive tranny?
I'm thinking I would rather have a known good tranny -vs- a junkyard one of unknown condition for the same money even if I have to give up overdrive.... Have heard that rebuilt 4l80e's are big bucks...

If I retro fit a TH400 what all will have to be done ?
reprogram computer chip so it doesn't look for tranny signals?

I'm not up on auto trannys- but isn't the 400 vacume controlled?
any kickdown linkage needed?

[odee]

the 400 has a vaccum modulator for shifting,the kickdown has a micro switch under the gas pedal or hooked to the linkage on the carb or tbi for passing gear. I would look into getting the 4L80 rebuilt.