Tf 727 modify or not
For street driving all that's needed is a quality rebuild and shift kit.
and a 2800 convertor,
and a semi-auto shifter that you can hold to say 5000.
and you may need a governor tune-up
But if you want to hit 5000, you'll probably need some better valve springs.
Why 5000?
Cuz on the 1>2 shift from 5000 the Rs will fall to 2950, putting your 318 350 rpm up the modest power-curve, and at least keeping up with the six-speed 4-banger in the next lane.
a 2800, for a 2-bbl street car?
Yes; Especially, for a 2bbl street machine with hiway gears. That convertor will turn her into a pretty good ripper off the line! But in this application, off the line to 20 mph is mostly all it's good for. But, if you think about it, that's a lot.