I've been looking at a '74 Javelin that is powered by a 258 I6 and a 3 speed manual.
I do not know what model three speed it is.

I have a nice 360 from a '78 Chief that is just begging to be dropping in between the front fenders, but I am sure that 3 speed would not hold up.

My question to the group, what 5 Speed would be recommended behind a mild 360?

It's my understanding that the I6 bellhousing should be work on my 360.

So, I would need a 360 flywheel, new clutch, pressure plate, throw out bearing, etc...
Reuse the existing clutch release mechanism (mechanical?)
Adapt a 5 speed (T-5 from a Rustang?) to the AMC bellhousing
Modify the rearcross member
Change the length of the driveshaft
Install a shifter if one did not come with the donor. (Hurst?)

Sure, I could use a T10 four speed, but looking to upgrade