273 for 318 swap advice

"however the tranny up-shifts waaaay too quickly and doesn't part throttle downshift as I'd like, so my next step is a shift kit. My choice is either a Transgo TF2 or the B&M transpak......any suggestions?"

Does it have a floor shifter or column? Do you have a tach? If floor shift, does it pull hard if you manually shift it? Sounds like the kickdown linkage should be lengthened on the bottom transmission lever. Double check the kickdown lever at the transmission. Disconnect it and make sure it goes all the way back when you mash the pedal.

Take the 318 but 302 heads need work to flow well. Your engine should be fine if you get it sorted out.