Im hooking a 400+ hp stroker motor to my 700r4 with 130,000 miles on it. ABout 20,000 miles ago i put a b&m shift improver kit in it. It shifts great with no slipping. Should i worry about blowing it up when i put the more aggressive engine in it? Is there anything i can do to the tranny that will strengthen it more? I was considering a kit from transgo but id like some advise first.

 

A shift kit will not make a tranny stronger...niether will the TransGo kit. They just modify the tranny for firmer shifts. The only way to make a tranny strong is to get stronger parts, more clutches etc.
My opinion...your tranny will last...for a while.
I think I heard one time (might be wrong...who really knows) that the stock tranny is only good to about 350 lbft of torque. Its really torque that will kill the tranny, not horsepower. If your pushing 400 hp out of the 383 (i'm assuming this is the stroker you are referring to) then I am sure you are over the 350 lbft of torque.
Get a performance tranny.

 

A Trans-Go Shift kit (when installed correctly) will improve the torque capacity of the transmission. Yes, there are other ways to improve the life of the transmisssion, but it must be torn down to do theses modifications. Another is getting rid of the stock torque converter and replace it with a 9.5" lockup TC. This removes about 15-17 lbs. of rotating mass, this change alone will eliminate parts breakage, and increase longevity & torque capacity.

 

I never new that the TransGo improved the capacity. I put the kit in my tranny a few years ago....I liked it....until my tranny went.

 

what kind of parts would i need to get to beef up my existing tranny? B&M has a kit in summit that has new clutches and stuff, are those the types of things im gonna need?

 

That's a start. But then you have to have someone put it all in...assuming you can't. If you can it will save lots of money. It would be nice to get some heat treated sprags and stuff also. But by then it would probably be cheaper to buy a performance tranny already ready to go. Pro Built can tell you more as far as that goes.....me, I just buy a tranny. From the feedback on this forum, Pro Builts are the way to go. I'll order one when my StreetFighter decides to go...(if it does)

 

Those are the types of things you're going to need, but never buy anything from B&M.