If you just want to keep up with traffic, & really just want torque then a small cam, a downdraught weber carby, a set of extractors & an electronic ignition system makes a bit of difference. I have nearly the same in my 210 wagon, but it's only an A12 with a stock cam & before it stopped working last Monday, it was quite capable of keeping up with traffic, generally just cracking the throttle to get away from an intersection, & lots of poke for a holeshot up the inside. I'll be replacing the engine with it's original A15, which burnt an exhaust valve a couple of years ago. The A15 will just get the carby, distributor & extractors, with the stock cam. When the head was serviced, I got new valve springs from a VW Beetle engine fitted, they cost $20 for the set & are comparable to the standard single springs.
Any engine swap will need a gearbox & rear end upgrade. Just upgrading the stock engine or swapping to an A14/A15 means you don't have to change these. Hopefully you already have a 5 speed, if not you might be able to get one of those to lower the revs at highway speeds.