You might as well save the $$ and go with an AOD. I'd take my chance on a cheap C4 from the yard before spending that kind of money. Stay away from the C6 too...heavy. Good luck!
I installed one of those TCI Streetfighter C4's in 1987, and it has been one of the best things I did to my Capri. Works like gangbusters, shifts perfectly.
It has about 165,000 miles and several dozen runs on it. Freshened it up in 93, with a TCI rebuild kit, and cleaned the valvebody. Put the TCI converter in about 91.
I also have a TCI valvebody, rebuild kit, and a converter in the 82. I rebuilt the trans myself, and with their parts, it runs great, getting into the 12's this year.
I highly recommend their stuff. TCI has outstanding tech support, and has answered every question I have ever had on the phone over the years.
C-4 is a hell of a lot better trans than a aod for performance. The rotational weight alone willl drop you a half a sec. The only way i wouldn't go with the c-4 is if you do a lot of hwy driving due to the overdrive. As for the tci never had any dealing with them but that definatly is not a bad price and is rediculus to say get a junk yard c-4. I build my own c-4's and i will tell you it is not the easyest thing to find the right one. Some are stronger than others and it makes a big difference. You have to know the ins and outs. The tci will be built to spec and have good parts including a reworked valvebody for more line pressure which is very important. A c-4 out of a junk yard will not be a joke compared to a well built, high line press c-4. I personally recommend a dynamic or J.W. c-4 as they both specialize in these. As for the price it probabaly will be more. I build my own and i spent over 1200 just on the good parts but mine is also rated for over a thousand hp. Had mine in for over 3yrs. with about 650 passes and still runs great. I'm only pushing around 300rwhp but thats a lot of launches with the front tires off the ground.
C4 is a great trans if you are drag racing. I don't care for TCI stuff. I build my own also. Running mid 10s with no problems.
If you are going to buy a C4 go with Dynamic, PA, or JPT. These companies specialize in C4s. Never delt with JW, but I think they have a decent reputation. TCI and other generic trans companies specialize in mostly GM trannies and they are not very good at that. I once bought a set of what they called "racing" clutches for a C4 from TCI. They were only your average Borg Warner rebuilder clutches with the same part number I can get locally at a MUCH cheap price. I think this is very misleading and I will never trust TCI or their stuff again.