Don't mix, period.

If you have a VW buy a VW reman head or buy 2 AMC from Boston Bob. He does
some modification to the valve assembly!!!!!

Mixing the head company will result in an unbalance engine, in every
possible way's (heat dispersion, compression, wear and so on. Even changing
only one head for a VW reman is not that good, you will bring back
compression on one side only, you are up for a "rings failure"on this side
or other severe long term problem.

You want to hear a horror story?

3 month ago I modified (I know the guy and he insisted putting this head)
an Honda (1.6SI) engine, the new head was from another company. Ring and
piston were not change. The result today is that the engine is cooked; the
rings and one piston have failed due to the very high compression from the
new head. The given specs from the company were not accurate.

Well this as nothing to do with VW, but it as everything to do with mixing
product/company that think that they up to the task.

I know that VW reman are not NEW and expensive and I don't know what I
would do in your situation, probably buy 2 AMC heads from Bob. At least he
tested those. But still, I would prefer buying 2 VW reman ,well I am not so
sure!!!!! I hope I don't have to face this situation soon.

A very good solution would be to find a use VW head in fair condition. That
what I would try first.

Well, that my 2 cents.
Ben
http://www.vwvans.com/
http://www3.sympatico.ca/huotx/engine1.htm