I have had a few different 10 second TB's and most of had 200's but my latest has a 400. I have had pretty good luck with the 200's I have had but I changed over to a 400 bascially for dependability. It takes a good amount of aftermarket internals and an experienced builder to have a 200 that will live long and do well in a 10.50 or faster car but with a 400 it doesn't take alot to live at that level and almost every town has a builder that can build a good 400. I am thinking I am going to try the Jake's transbrake valvebody in my 400 next year that retains a forward shift pattern and full automatic operation. I also have a Gearvendor for the 400 so that I will have OD.