My 40 IDFs have had it...they were complete contaminated by a careless PO, are very old and even after a rebuild, are still siphoning fuel and hard to tune. They are made in Spain, so that might be a clue to their age.

What is the best option for new or rebuilt IDFs--and even the notion of rebuilt scares the bejeezus out of me?

Yours are the best ones to have professionally rebuilt. The new ones are junk.

I have their kits twice. Actually three times. https://www.cbperformance.com/product-p/6456.htm

Carbs Unlimited in Washington. Best price I could find on made in Spain Webers.

Are new "Made in Spain" webers no good compared to say 1970s Made in Spain Webers?

The new Empi HPMX's are very nice and have had the bugs ironed out of them compared to the 1st gen ones. You however will still need to clean them completely and recheck the float levels prior to install.

They have also removed the enrichment circuits in them.