I need to have my seats redone and I spoke to an interior shop who told me to let him build the seat foam under the new seatcovers instead of buying the reproduction foam from one of the resto houses. I thought it would be better to go with the repro foam already molded to fit the seat frames and covers, but this guys tells me you will have a better seat by building the foam from scratch. Does anyone have any experience with this? Appreciate your comments.

Just my opinion, but if this guy knows his chit and says he can do it better than aftermarket seat buns, let him!
The reason I say this is because new aftermarket upholstery and new aftermarket buns are NOT made for each other. Ask me how I know. ;)

If you let him build the foam/buns himself, he'll create them to fit the upholstery, ending up with a much nicer finished product. I'd say go for it.

I have that project coming up, Was the repro that far miss matched Joe? What repop co did you use for both?

Well, I bought deluxe PUI upholstery and deluxe buns for both buckets, from Ricks. The buns came in a box from -COUGH- a place called Mustang something-or-other! ???

The buns for each seat were from different manufacturers actually, because they looked different from each other as far as how they were made. The foam was molded exactly the same, just looked different.
The PUI covers fit loosely in certain areas. Not a big deal as I bolstered them with polyester batting anyway.

Now, the fabric pulls on the underside of the upholstery that you need to slide the wires back into, and then push through the molded slots in the buns in order to hog ring them in, didn't match each other perfectly. It was a struggle getting the covers and the buns matched up before hog ringing them on. But hey.... this is aftermarket parts we're talking about.

I can't complain about the PUI upholstery quality at all. Or the buns. It's just that they don't and won't match each other when put together on a seat. I can throw some more pics on my site one of these days so people can see them. If I'd had a shop do them, they'd have turned out a LOT better, I'm sure. But I wanted to give it a shot.

I had a buddy that does upholstery to my seats using existing covers but I bought new springs. He added the pad instead of burlap and they beefed up the foam for me since Im a 'bigger' guy :)
Turned out nice. Next time I bring in the seat he will install a lumbar build up of harder foam so I dont have to use a rolled up towel for that lower support. Give a local guy some idea how you want it to 'sit' and let him do his work if he has good reputation.
:)

I guess my concern would be that if the buns are built from pieces of foam instead of molded, that they might not have the correct feel and fit for the houndstooth seats.

See if the guy can show you examples of his work. Ask for references, and whether he has automotive seats done already that you can see.
It's a perfectly legitimate request.

I ordered my new deluxe seat covers as well as replacement foam from Ricks First Gen and was very happy with how everything turned out. No differences in the foam, installed nice and has held up just fine the year and a half its been in the car.

I did my seats in 2001. PUI covers and foam from Rick's (don't recall the manufacturer). I redid the wires in the seat bottom amd put in new burlap. I added three pieces of foam pad to the bottom of the bun, leaving the slots open for ringing. Everything fit tight and has held up perfectly for over 4 years. The wife just won Best Interior at a show about a month ago.