I maybe wrong but wouldnt the spacers be like adding +2" arms? - making the shocks softer or maybe to soft? Then causing the need for better shocks? plus the added strain on other parts.
How much different are the frames?
I would move the mounts on the older frame if you can weld.
I thought I saw a post on here about 400ex arms fitting - maybe. Maybe other arms would fit also. If you moved the mounts you could put on whatever arms you wanted . You might find some nice cheap used ones and just make them fit.
Or get a newer frame. Check craigslist