273/ 2 barrel camshaft options

As the vaaast majority have indicated, myself included, the E-4 cam would be an ideal choice.
Manufacturers produced engines with different ratings; high output, or high performance versions, 2bbl & 4bbl etc. So the E-4 would be a nice step up, with no problems.
Majority of lifter/lobe failures in recent years is from poor quality lifters: wrong radius or poor metallurgy.....or both. So having your factory lifters re-faced will avoid that problem; if your engine builder disagrees, find another engine builder.....
New valve springs are a good idea. If you re-use the existing springs, you might get valve float. The E-4 has about 0.020" more lift so that in itself than the stock 2bbl cam, so that will help ward off valve float if you use the old springs. Really depends on how 'tired' the springs are.
The two centre exh springs are the ones that often lose tension from the heat concentration from the centre exh ports. Any spring that is shorter in free length has lost tension...