Tom,
In PA emmisions are tied to the chassis model year. For specially constructed vehicles that is the year the chassis was manufactured - that means current year usually. It is not the year the chassis copies, e.g. 1966.
First time registrations are, according to code, exempt from emmisions tests, in following years you are exempt provided the mileage is less that 5000 miles per year. If you exceed that, you can still get an exemption but you have to spend a minimum amount trying to correct the problem before you can get the exemption.
Here is the PA emmisions code section for subject vehicles:
http://www.pacode.com/secure/data/06...bchapBtoc.html
Hope this helps,
Jim