What is needed to build a 7 second (1/8th) street car

The MPH is weak. No way it's making close to 450hp. More like 375ish. 450 at 3400# should be almost 10mph faster in the 1/8

Look at fuel system (where lots of in-car lack of performance issues are rooted) and timing as well. If you can jet it up and it doesn't change the MPH, you likely have a delivery issue.

Shift point doesn't sound bad if it's got a decent duration roller in it.

340's like gear and lots of converter. If this is a race oriented piece, with a 340, I'd have a 4500+ converter. The 3800 may work ok hitting juice of the line.

With a 28" tire, I'd have a minimum of 4.56's in it. Hitting it with 150 shot, maybe 3.91 or 4.10's especially if you a smacking it on the hit.

Unfortunately right now, the chassis/converter is VERY inefficient.