Since you already have the big lens, you only need a camera. A 7 will accept the lens, of course. There can be a bit dimmer image in that VF, and the meter probably won't work accurately. The later 7s/sz will usually have a better VF image, and may have a working meter. The shutter curtains in any will almost always be wrinkled. As mentioned, unless badly wrinkled, this has little to no effect on camera usage. The less wrinkle the better, of course, but a slight wrinkle is perfectly normal and acceptable. To attempt to find perfection will be costly, and you will probably bend the curtain yourself on the first roll or film or two. It is very easy to do, and the curtains are very thin... but also very strong.
Ritz Camera sometimes has early Canon models. I mean the website, not the shops in the malls. I did buy a hood from them, pricey but also rare and hard to find. KEH is a good place, partly because of the warranty and return policy.
Kevin can be pricey, but also usually has very fine stuff. Other dealers are very spotty, as the cameras aren't really that common, except the 7.
You should be looking for a presentable camera with no major flaws and a slight wrinkle, since it will be one that will be used, rather than a shelf-queen.
I've found both my 7s models and my 7sz through eBay, without problems. One of the 7s is used along with my M3, and they are fine shooters. It has the slight wrinkle, and that affects nothing.
If you are fairly patient, one will turn up. Chasing close to mint/perfect curtains will not be easy, but will be very expensive. Advise is easy, but I also speak from some experience.
Harry