Ok, first your compression ratio on an early 273 is about 9:1. You do not need "better" heads, pistons, or anything else for your 273. Second, for a 2 barrel 273 the small Racer Brown cam is perfect and a small step up from the stock 2 barrel cam. I have an extra new custom Racer Brown cam just like the one Eekvonzipper used. Notice the duration @ .050 is 200 degrees. It is a better choice for a 2 barrel engine and still quite nice for a 4 barrel intake and carb. Eric has a nice build, he started as a rebuilt 2 barrel 273 and just added the stock 4 barrel AFB and 65 intake. You can get a set of 16 new solid lifters for $50 and a true roller timing set for $80 from Hot Heads, the early Hemi racing people. I would also suggest running at least stock 360 valve springs and Felpro positive viton valve seals with the above cam. I'd also get your distributor recurved by Halifaxhops.
[URL]https://hothemiheads.com/cam_shafts_timing/lifters.html[/URL]
[URL]https://hothemiheads.com/cam_shafts_timing/timing_set_true.html[/URL]