I am the proud Owner of A 1966 Chevy Biscyne and have recently rebuilt a 350 for it. I am currently running a TH400 tranny but am confused on the issue of 4 speed manual transmissions that will work with my motor any help would be greatly appreiciated

Well if your car already has a manual tranny setup than a ive been told that a strait 6 3 spd manual trans will work just as well on most small block setups i mean i could be wrong but it does not hurt to ask around at shops or even at the track.

Newport

If you have the clutch pedal set up, this swap shouldnt be that hard. You should have lots to choose from.You could probably find a muncie, or a cheaper unit a saginaw, could be found at just about any swap meet. 4 spds came in everything from chevelles,corvettes to camaros of the early 80's i beleive.I think that a 5spd form a 3rd generation camaro will even go in without too much work ( Not sure though) But as far as the bell housing, if its from a small block or a big block it should work. look for a trans out of a car though.You could even mate a newer 6spd to it ( bell housing from weir hotrod products, hydraulic throw out bearing, shifter sit @ 4" back from original 4spd set up)More labour intensive, but not out of reach. The easiest swap would be a 4 spd, though .70 to 72 chevelles had a shifter which was mounted same as the rest but had a dog leg in the shifter handle, it allowed the shifter to be placed into a centered console.But for your application the shifter would poke through the floor just left of the trans tunnel.If you visit the year one sight you may even be able to get some pictures of this set up. They will also be able to sell you the proper shifter boot, cross shaft and pivot ball etc., to make it all original looking.Hope this helps .
good luck