1963 Dart 170 Slant Six question

I may be picking up a 1963 Dart 4 door sedan next week (assuming it is still for sale).

The car is a 170 Slant Six with a 3 spd column shift.

Since this thing has that #$%^*& non synchro low gear; is there a 'bolt-in' 3 spd from, say a 1970's A-F body that would replace it? I realize I may need to switch out the bellhousing.

Too: would fitting the 225 Super Six intake/carb be worth the effort for a bit more power? The present engine seems to be tight (no smoke), just a slight miss which may mandate a valve adjustment.

Needless to say: those nasty ol' 9" drum brakes with their attendant 5 on 4" bolt pattern 13" wheels will disappear in lieu of the 1973+ disc brake swap and matching rear end (even a 7 1/4" would suffice).