suggestions for my 340?

Factory rear gear ratio was 3.21 for an 8 1/4 even in 340 cars. that is a very short tire and steping up to a 275-60-15 or even 225-70-15 (only need hieght not really width unless you like fat tires on the back) and 3.55s and sure grip will greatly help you.
Sure grip is for fun :burnout:

Also changing the intake to an LD340 or just an eddy performer will help as it is better than stock and is aluminium