I think it all depends on what the "etc" in #2 is and what the comfort level on replacing parts and/or rebuilding is.

Maybe more than #2 with some hose replacement added in; maybe less with not replacing the compressor and only R&R'ing the clutch and a seal a la Funola's writeup from last summer.

I'll assume (against my own advice) that since the OP has cans of R12 and has a manifold gauge that fit and appears to know how to use it, that he knows he has R12 fittings and the system doesn't appear to have been converted to 134.

So, yeah, don't just put the R12 in and hope. But don't assume a specific list of parts yet either.

For example, I'm no expert but I've read that the expansion valves should match the refrigerant used for optimum operation. I don't think they make R12 TXV's anymore, so a new one would be R-134a. Is it enough to make a difference? I don't know and probably not, but if the existing valve is okay, maybe just new o-rings. (Some good theory on the TXV here: http://yarchive.net/ac/expansion_valve.html)

There's the difference in the sump/oil well/X-thing on older M-B compressors and new R-4 replacements since M-B compressors are upside down. Again, a significant difference? Maybe not. CompressorWorks says their 'new/updated' R-4 compressor doesn't need the extra lube; but anecdotal reports of Four Seasons compressors says they fail early because of this.

The OP's post count is low, so he may not be aware of the wealth of info and peculiarities of some of the W123 A/C components.

Do a little research, inspect the system and be prepared to go for #2 - or even more. Leak check - vacuum and pressure - have a plan to recover the R12 BEFORE putting it in, just in case, then go from there.