11'' or 10'' converter
 

what would be better a 11'' 2500stall or a 10'' 3000 stall converter on my 69mach1 408W, with full manual c-4, 380ft lb's@3100, srteet driven some track.

Being predominitly street i would say the 11" with a 408 it will also give more then the advertised 2500 stall speed.

Your best ET will happen if you can get it to stall right at peak torque. But it might drive better with 2500. Might even launch better, a little easier on the tires.

" srteet driven some track."

Sounds like a lot of car to be driven on the street all of the time. Bet it is a monster!

But I would go with the 11'. It will make it easier to live with on the street. But realistically with the mods that you have listed, and the car that it is in. I don't think the 10' would hurt your streetablity anymore then you already have. Just make sure to get a HUGE tranny cooler with the horse power you are running and a 10' converter. The temp is really the biggest difference between them.

Rear axle ratio?
 

What rear axle ratio? Or did I just miss it? The main consideration for the street is that you want the cruise RPM to be above the actual stall speed. Otherwise you're slipping a lot at cruise with lots of inefficiency and heat generated in the tranny (not good).

Rev

10'' or 11''
 

3.50 posi rear.

11" 2500 stall
 

I'd run the 11" 2500 converter. With the amount of low end torque you've got and the 3.50 axle, you won't need too much stall anyway assuming your car is not really heavy.

Rev

10'' 11''
 

Thanks rev, think i'll leave it alone, i was going to bump up the cam a few, mine now is small for a stroker 218 228@.050, lot of torque down low for street.