I have completed the repairs, and the speakers are working well once again. In case anyone else has these speakers, I thought I'd post how things went.
I got the 8" angle attach Cerwin Vega (red, as they were a bit cheaper on sale) foam surrounds and screen/mesh type dust caps. I had a hard time deciding between angle and flat attach, since the lip of the cone seems somewhat angled but then flattens out towards the edge. In the end, it seems that angle attached worked fine. I wasn't sure what kind of dust caps to get (paper, plastic, screen) but decided to stick to the same type (screen) as the originals. The originals looked like they were about 2 1/8", but these were not available, and the 2 1/4" were out of stock, so I ended up getting the 2 1/2" ones. They seem to be fine. I ordered from Speakerworks as they had the best overall price with the shipping to Canada. It came to around $33 USD total. It took about 2 business days for the order to be filled + 5 business days for shipping, so I received it in a bit under 2 weeks.
While waiting for the kit to arrive, I removed the speakers from the cabinet and cleaned them and removed the old foam. This was the worst and hardest part of the repair, as the glue was very sticky and messy even after all these years. I went slowly, peeling off the glue off of the cone's edge with an exacto knife. I used a flat screw driver as a chisel for getting the old sticky glue off the basket's rim. Although some recommend using alcohol to loosen the glue, I found that made more of a mess, and that I was better off just scraping it off dry. Am I ever glad that's over...
I also removed the dust caps by cutting them with a knife around the edge. I had initially tried to use a hairdryer to heat the glue in the hopes of prying off the dust caps without cutting, but it wasn't making good progress and I worried about melting/damaging the glossy coating on the cone. Cutting worked much better. I experimented with various paper thicknesses to get the shims right. It was trial and error, but pretty easy.
Once I received the repair kit, the rest of the repair was relatively easy. Applying the (white) glue to the surrounds and cone edge and matching them together went well, but after letting it dry about an hour I noticed that only the very inside edge (some places as little as 2mm) of the surrounds were attached to the cone, so I applied more glue between the surrounds and the unattached portions of the outer edge of the cone. That seemed to work well and I am now more confident of the repair job. Gluing the outer edge to the basket was easy, and afterwards I installed the paper gasket and flipped the speaker face down to allow it to set and dry overnight. This ended up also gluing the gasket to the surrounds and basket just from the spillover glue.
Thanks to the shims, the cone was well-aligned and there is no voice coil rubbing.
I simply re-installed of the speakers into the cabinet (without forgetting to reconnect the wires correctly!) and they now sound as good as new.
Less than $35 to restore the enjoyment of these speakers, plus some fun in repairing them; I'd say that was a good deal. Thanks to Robert and these forums for pointing me in the right direction.