they are good trannies but if you have gears stay off the highway, My father has a C4 in his 351 falcon with 410 gears
runs great at the track but can only do 50 on the highway and it's screaming.....he can easily blow my doors off but I tell him "lets do a mile run on the highway" then he just clams up, hahahahaha
This is true, but back then the speed limit on the interstate was only 55. Still I would say it is streetable. Just may not be the best choice if you make long cross country trips.
Plenty streetable, but if you will be doing any interstate driving, I wouldn't go with anything higher than a 3.50/3.55 gear. If you will be doing a LOT of interstate driving, I would forget about it, unless you don't mind really mild gearing.
If it will just be an around town car with some highway driving, you could get away with a 3.73 gear. You can go higher, but it is pretty annoying IMO. Swapped from a 4.10 to a 3.50 in my '65 for just that reason.