Diesel Bombers - 4r100 making it last?

my transmission slips in third gear on hard acceleration but it seems more like the tq converter, its lazier all around an the trans only has about 12000 on it, stock rebuild when i bought it. i noticed it got sluggish after a tractor pull lol. i pulled stock class and had to be a macho man after beating the dmaxes and a few dodges and inches from my friends cummins, so i signed up for the open class, the sled was wayy too heavy that time, then my tranny felt sluggish after that day, it still drive fine though, never gets hot. so for where my truck is at now i am thinking of puting in a decent triple disc converter but not one thats going to snap a shaft hopefully, and a valve body from john wood or bd with new fluid and filter obviously. if i do this and dont hit any tractor pulls should it be decent until i can afford a 5000+ dollar trans that everyone is going to tell me to buy when responding to this?