The TEAC Model 5 originally came out in 1975, and is an 8x4x4 mixer. I there any particular reason why you are going for these dinosaur mixers?
If you have an eight track tape deck, any mixer with eight inputs should work well with it.
There is a *huge* selection of used mixers on eBay in the $100-300 range. I see no reason to get locked into one model so quickly.
Go to the musical instrument category and type "mixer" into the search box. When you get the results from that, look further down the column to the left, where it says "Items Priced". Then enter something like $100 to $300. You'll come up with about 1,500 results.
I think I see the TEAC Model 5 that you are interested in. It doesn't look bad, but if you can sit and watch the auction for a few weeks, I think you might find something a little newer that will work as well or better for you.
Also, don't rule out a new mixer. You can get a Yamaha MG 16/4 for $279 and have a brand new mixer.