So, you're asking if you should get an E34 M5 now, and get an E39 M5 as well with the E39 taking a few weeks longer due to the outlay for the E34?
Do you have the patience to wait until another Royal Red model shows up should you not get the one you're looking at? And how far will you travel to find the right E39?
I will say that you should go after whatever it is you want and not settle for anything else. I kept looking for the right M-Sport for 2 1/2 years and I'm glad I did. I almost went for a 740i Sport, but didn't find one around here that fit. Then the right M-Sport came up for sale later. After a 3,750 mile trip to go get it (and 3,750 miles back) it was more than worth it. Still to this day happy I didn't buy an M5 that was tempting, and didn't find the right E38. Because I knew what it was that I wanted and waited until it was available.
I've found a 2000 in Alabama, a 2000 in Maryland, and a 2001 (listed as "burgundy") in California. Didn't check Canada. But as there's 3 of them I found with a quick check in the US they're out there. Incredibly rare, yes. But you can still find one. Actually didn't know they came in Royal Red. Have never seen an E39 in that color. Did see an E38 in Royal Red and thought it looked pretty good. Was interesting to see that E39 M5's Royal Red is rarer than Imola Red, while the opposite is true of E38's.
FWIW, it's not uncommon of me to see the guys on the M5board say they enjoy the drive of their E34 M5 better than their E39 M5. They seem to like the rawness the E34 has, that the E39 lacks. Apparently the E39 makes for the better DD, while the E34 makes for the better weekend fun car.
Cosmos Black/Black 1995 540iA M-Sport
BMW Individual Exclusive Edition, 1 of 65 total, 9/25/95 Build