No doubt about it you have to tack the end's to the crossmember. Remember the steel on the crossmember isn't too thick so don't over do it. Insure and check there is clearence between your crossmember and the TKO though before you weld the end's in place. They can not rub as it can damage the Transmission.
which tko did you get. im gettin the tko 500 pretty soon and i talked to holcomb motorsports and they said that you can either buy the new crossmember and install that or just move the original one if you have to. they didnt say anything about tack welding the new one. hmm
The new one may already be set (Welded) in place for use with a Tremec. Stock Ford Crossmember's require grinding the old weld bead off the end's, adjusting to were the Tremec clear's and then welding the end's back in place. I know the crossmember from FRPP is a knock off of a factory crossmember and come's with the end's loose and ready to adjust.... when you have adjusted them to were the trans clear's you just give them a couple tack's and your set. No matter what crossmember it is, the bushing end's HAVE to be tacked to the crossmember... they can not just be left loose.