Grooving the shaft is easy with a dremel and a cutting disk, just smooth out the corners.TA shafts had diagonal grooves, 273 had straight cuts iirc. Mech and hydro pushrods are too far off to interchange. Just get the correct ones. You can cut down slant pushrods to use on 273 rockers, just remove the hardened round tips, cut to size and press the tips back in. They are captive once they are installed so they dont need to be uber tight in there but will press in snugly.