The VW/Audi heater sounds good except for one thing, the Windsor pipe nipple is an interference fit and not screwed in. The earlier ones did screw in, they had a hex against the block, but not the later. I once tried on a junk block to get the nipple out, even had a 2 foot pipe wrench on it, but no go. I didn't care on that block, it was total junk, but it taught me not to try that on my hot rod engine.
I don't have much room for a filter, since it's not a stock installation, I can just barely get a short filter in.
So I bought a right angle adapter from the scrap yard off a 460, but the bolt is a male to go in the block, like the early Windsors. DUH, I should have noticed. So the 460 this adapter came off had the nipple threaded into the block.
I'll use a right angle adapter along with the exchanger, and get it from the racing catalogue I guess. Your picture shows what I want, if the bolt screws to the nipple, like filter screws on.
The one for the Duratech that I lost was an idea I had for my wife's Duratech Taurus. She does really short trips and I thought it might be better for the oil to be heated up quicker.