Report borg warner to th350 in 1965-83 Avanti Posted September 5, 2016 · Edited September 5, 2016 by fred88 so i was all set to do the 700r swap on my 1969 avanti rqa0319 but was recomended to do a 350 turbo tranny as i am pushing 400-450 ponies now with a cam, exhaust, ignition, manifold, headers, carb, etc. has anyone done this? it seems the 700r is more popular of a swap, but if the 350 is more robust and slightly smaller and cheaper why isnt it more popular? Because the 350 isn't any stronger than the 700, the 400 is, but not by much. If you plan on actually driving your car, not just racing it, an overdrive makes more sense. You can use a higher ratio rear for your burn outs, and drive down the freeway without running your expensive to replace engine at 4000 RPM all the time. Since you have an Avanti, I think you would be better off with a 200 built to your needs, no clearance issues, no fiberglass tunnel modifications. Remember to check your rear end max torque ratings also. Nothing worse than spinning the splines off an axle--if you're still running the old Dana 44 tapered axle rear, that only has 19 spline axles and will probably shear off a hub pretty easy at that HP range. Fiberglass doesn't do well with a rear wheel going missing or coming off at 90.