OP, you need to have some imbalance in either the TC or the flexplate with the 360. )One or the other, not both.) You could keep the present TC if you used the imbalanced flexplate. Here is one for the 727; there is a similar one from B&M for the 904. These are good items and run about $100. B&M 10236: SFI-Approved Flexplate 1971-1992 Small Block Chrysler 360 with TF727 | JEGS
Or, you can weld a weight in the right place on the TC.
One advantage to changing the TC however, is that the 'snout' of the TC will be smaller on the 273 than on the 360. So, if you use the present TC, you would need a small ring shaped spacer to go inside the crank register (the hole in the back end of the crankshaft). Some members here offer them IIRC.