3.55 or 3.73 gears in 66 dart gt

Another thing you could do is more stall so to start in/nearer to the main powerband, go with lower 1st & 2nd gears 2.74/1.54 vs 2.45/1.45, or swap in a OD tranny get all that.

I'm sure these are more than you want do, but if you got the cash and desire it will get the most out of the 273.