Hey so the car is a s10 used for drag racing mainly

Lq4. 10.5:1 compression n/a
317 heads
227/235 .616 .614 115 Lsa
Th400 foot breaking

Gears are 3:42 (planning on swapping to 4.11)
It has a used converter that was supposed to stall at 4000 rpm but it foot breaks to about 2500 or less.
Ran a 7.7 in the 1/8 at 91 mph. Lars weekend..

I'm thinking there is an issue with my combo. Is my converter short or are the gears working against me?

 

Sounds like the converter needs to be reworked.

 

Would a 4000 stall work best with that cam and in a 3000# truck?

 

I think so. My 4k is working pretty well for me.

 

How much would a bad converter effect my et?

 

No clue but it looks like your 60ft is suffering based upon the numbers you posted above.

 

Going off the information you provided it sounds like your converter is too tight. the new gear will help the car for sure but it's going to tighten the converter as well.
What other information can you provide about the converter and the car?
weight? estimated HP? converter make/model number? advertised stall of the converter.