I bought a 13-piece heater and A/C box and seal set with application for 1968-1972 models with A/C from Year One, part number DL558 (see picture at http://www.yearone.com/serverfiles/part.asp?pid=DL558&c=0&e=0&cat=0&hid=016AE48124). The kit comes with a single photocopied page that shows the heater box, the a/c condenser blower box and heater core but does NOT clearly show where all 13 of the supplied seals are supposed to go. No one at the part suppliers know where they go. I went as far as contacting the manufacturer who said that the diagram was created 20 years ago and no one at the company knows where the seals go.
My 70 Chevelle heater box appears to be missing many of the original seals so it is not as easy of taking it apart and replacing what is there.

Has anyone used one of these 13-piece kits and has the knowledge of exactly which seal goes to which component (and where it goes on that component)?

Thanks!!

I got a kit like that from OPG and it had NO instructions. What I did was study how the system seemed to work and look for where a seal could go that would contain or block air leaks while in A/C mode or heat mode. There is an approx. 6" x 1/2" rubber seal on the flapper door that you need to make sure is in good shape. The main A/C Box gasket (runs 90° to firewall gasket) and the firewall gasket, I ended up using 1/4" foam weatherstrip. Get the black or hi-temp version - not the household stuff. What was in the kit didn't line up properly and I wanted a good solid seal at the firewall. If you have any GM assembly manuals, you might find some info there. Good luck!
-Bill

I used that same kit and promptly threw most of it away! I only found 2 or three that actually fit where they were supposed to go. I used windshield sealer (that you can buy at AutoZone for around $14.00) to attatch both 'sides' of the A/C box together and to attatch the whole box to the firewall. The stuff is very easy to work with and fairly easy to clean up. My car appeared to have most of the original seals still intact (on the inside) so I didn't mess with any of that.

Hope that helped!