Sounds like a nice car. Have you decoded the numbers? A T-350 was not used until 1969. In '67 it was a 2 speed automatic used with an OHC 6 cylinder or 326, or a T-400 if it had a 400 engine. [A buddy's car was a 1967 400 w/T-400 and 3:08 rear gears. A great combination] Later low compression 400's used the T-350. Any Saginaw, Muncie, or Borg Warner 3 or 4 speed manual trans can be used with the 2 speed automatic/ T-350 cross member, the T-400 is different. They will all bolt up to the BOP manual bell housing. Get a new forged steel flywheel. Most used factory cast iron units will not pass a magnaflux test. Steel is safer and won't explode. With 3:08 gears [great for highway mileage] you need a manual trans with a decent first gear. I try to shoot for a 10 to 1 overall ratio multiplying the first gear with the rear gear. That is best for easy take off especially in traffic. Most Muncie trans have either a 2:20, 2:52, or 2:56 first gears. They need 3:73, or 4:11 rears to work well. The more common wide ratio 2:52 multiplied by the 3:08 rear gets you 7.76 overall ratio. You will be riding the clutch just to get going even with a 400. I had a 3:08 rear in my 1977 TA, 400 engine, but with a Super T-10 trans with a 3:42 first gear. Overall ratio was 10.5 to 1 and I could climb a tree with that car. At 60mph it was 2000 rpm, perfect. Do the math and you will find a Muncie is best for racing and street fun. Overdrive trans is best for highway. Before overdrive GM used big first gears with highway rear gears to get a good compromise. That is why the Saginaw came with up to 3:50 to 1 first gears. I have that exact trans in my G-body wagon right now. It has a 3:23 rear, 11.3 to 1 overall ratio and I use it for towing a boat. The 301 engine loves it, but a 400 will work if you don't abuse it. Lastly, BW ST-10's came with a lot of different ratios. The average guy can not tell the difference between a Muncie and an ST-10 so no one will know.