I had my alternator redone and up graded for my 69Z and the front half was replaced with a new piece without the numbers on it (original top bolt boss was broke off at the hole). Would it be a no no to try to have the numbers put back on it? Would not having the numbers hurt the value?

If the broken alternator was the original 837, I would seriously consider getting the ear repaired. Those things are going for crazy money!!

It is OK to restamp the numbers on the replacement, as long as you are up front about the restamp. If you are not, you will throw the pedigree of the whole car into question.

In my opinion, a Z with an unstamped alternator, and the same car with a restamp are worth aobut the same. ($100 more, at the most.) However, if you repair the original 837, you are adding at least $500, maybe $700 to the value. The big thing is that the original alternator is an example of attention to detail, which probably extends to other areas of the restoration.

oh, btw, I would use the original nose, even with the "upgraded" unit, which I assume means higher amperage.
I was planning to use the nose off an 837 for my 63 amp alternator(I have a Yenko clone with A/C) However, after seeing the high cost of an 837, I decided to stick to the 843, which is correct for big block with A/C. I rationalized that while A/C was not an option on L72, the A/C system is completely correct for 69 B/B.

Thanks for the reply unreal. Unfortunatley this unit was done a few years ago and the front piece is long gone. I really wasn't aware of the importance of the 837 number until just recently and had no idea what I had or if it was even original to my car. I just assumed that since that part was broken i could have it replaced and with the knowledge i have now...well, lets just say everyone line up and kick me please.

My 06A Z is unrestored and isn't completely original anyway and probably will never be due to the outrageous prices some of the parts are commanding. I have all the original internal engine parts, but not the original block, based on the number by the oil filter boss, no carb, and a suspected restamped distributor from the previous owner. Trans is a May built M20 with the wrong VIN on it, and the 12 bolt rear is a 11.28.68 build with 4.10's. I'm working on replacing this rear with a unit dated in the mid April 69 time frame with someone that frequents T.C. that needs my rear.

So you see all I can afford to do is get the dates a little more in line but not have the correct VIN stamps. Whether this is good or bad I don't know, but it will never be numbers matching.