Stock up through 68 used a 4.22 and if you have a 948, stick with it.
69-78 used a 3.9, late 78 & 79 used a 3.77.
And if you really want to leap off the line, Morris Minors had 4.55s and some had 5.30s I think) zero to 40 in 2 seconds, but no faster :wink:
I currently run a 4.22 with a 5 speed and I think that is the perfect combo.
My 676 runs a 3.9 but has the stock 4 speed, it's nice for country drives but I also have a 1275 in it so the taller diff sort of matches the larger engine.