Rebuilt my first rear end ever and it works. Did it all with the axle still in the car, which I don't recomend but had to do everything by myself. The Ratech spacer takes a while with the trial and ERROR of getting it shimmed properly but it worked awesome. Especially since there was no way I could get enough swing on a strongarm for the crush sleeve. I highly recomend this simple little part to anyone who's gonna rebuild a diff.

I see you are from Canada!

Where did you get it from?

I order a lot of stuff from Summit Racing. They hit pretty hard with shipping and handling for stuff coming across the border but they usually have it in stock and they're shipping is fairly fast. I hate to wait so in the end I guess it's worth it. I find most places in Canada are concentrating on those annoying little whipper snipper cars.

Is the solid pinion spacer a proven piece? I have one in my car and am afraid to really stall it up hard and launch. Right now I am easing into the throttle and pulling 1.51-1.53 60 foot times.

Yes, it's a proven piece. Hard launches compress your stock crush sleeve more, giving slack, making it do a "hammering" motion after that which will help destroy your gears. This can never be compressed, you just use the shims they give you to get the right length, rather than crushing it. They're discussed on this forum a bunch if you want more info, just search "ratech". That's pretty much the only part that company makes for us that's talked about on this board. Or solid pinion spacer.
You can just buy the right size piece of tube and cut it to size in your garage. If I had known how simple of a piece this was I would have just made one on a lathe and not paid for it.

Summit was out of stock when I bought my pinion spacer. 4111 is the part # IIRC. I bought it direct from Ratech, just called 'em up and got it sent to me. Airmailed via fedex and whatnot totalled $70, and the part was only $21.

I read somewhere (maybe here) in the late 60's this type of part was in the race kits supplied by GM to the "non factory" race teams.