Nice looking car and let me wish you the best on your build.
One thing I would hope you would revisit though is the 200R4 option. The 30% drop in rpm will come at the worst possible time, on the big end of the run. Also the lockup clutches are a weak link and I wouldn't want to use them under full power if you are making any power at all and you sure should be with the turbos. Also the 4th clutch pack is not real strong.
For instance at WOS after we got Sparky in the 300 mph Club I decided to run my truck in the 130 mph club. I have 28 inch tires, 3.50 rear gear and a 700R4 with the 30% over-drive. The truck ran 85 mph at the .2 mile and over 105 at the 1/2 mile, but was geared to low to run the 130. I ran 124-125 at the mile, but my problem was I was taching 6000 rpm there and my cam is all over at 5500, so I was on the wrong side of the power curve at the end of the mile. All of the runs were just using 1st, 2nd and 3rd.
I tried over-drive for one run and it was pulling it, but too slowly and that run resulted in 118 mph. I have my converter lockup wired so that I can turn it off, turn it on so it locks in 2nd, 3rd and 4th if I want and also so that locks and unlock automatically going in and out of 4th. I considered throwing the switch and locking it once I was in 3rd and believe that would have given me the 130 as the converter is fairly loose and was slipping 400-500 rpm in 3rd under WOT. I then decided it just wasn't worth it to take a chance blowing the converter lockup clutch since I need to go to Calif. in November with the truck and didn't want to have to replace a converter and possibly a transmission.
I had a 4L80E built by Crosley (on here) that should be good for 700 HP and that with a 3.20-3.25 Ford rearend will hopefully go in the truck over the winter. With that gearing I should be able to run the 130 with the present motor and hopefully much more if I still go ahead and turbo the motor and use some 2.75 or 2.47 gears I have for the Ford rear-end.
Anyway if you can't afford something like a G-Force, Gerico, etc. for the car I would look at a close ratio Muncie for the car along with a Ford rearend and maybe a couple different ring/pinion combinations. We ran over 600 HP through a Muncie in Hooley's Stude for the first couple years and it held up.
Here is a link to a 13% over-drive option for the M21.....
http://www.riversidegear.com/categories/muncie-4-speed/products/product-166.html.......... that could be a pretty slick option if it is strong enough.
Here is a link to 700R4 stuff on my site and a lot of the lockup stuff applies to the 200R4 also.....
http://purplesagetradingpost.com/sumner/techinfo/techinfo.htmlc ya,
Sum