viking makes an 11 inch and I'm guessing Pfaff does also. For Viking, it's the Saffire series as well as the Tribute 140, which was an anniversary model and probably not too many of them are available used. The Viking Diamond, Ruby and Topaz also have the 11 throat but they are also embroidery machines. There are used ones out there.

I bought a KenQuilt for $1000. I don't know if it is vintage but it sure is old. Only quilts from the back but once you get used to it is OK. Quils very good it is 11.5" by 5" and is very low key..I found it on Craigs list in So. CA. Have had it for 6 months and it has been used quite a lot. I am hoping to upgrade in about a year...I learned on a newer Nolting so using vintage is not very much fun, but it will do until I have more$$$.

I'm sorry, I didn't mean to just talk about me, me, me....I told my story because there are different places to put out the work and some LQS or quilt guilds might be a good place to start.

Yes there are "vintage longer arm machines" Look for a commercial sewing machine. They have been around for years. I also believe they can be modified to make them run slower since they were set for fast speed. A few years ago I saw a Brother that had about a 14"(?) area. It was new. Consew is one brand for industrial/commercial machines.

Janome New Horizon has an 11 inch harp. i just got through looking at one. They are coming out with a newer machine so you should be able to get a good deal on it right now. My LQS offered me theirs at a 500 dollar lower price. Didn't take them up on it but you might get a better deal that that.

Bailey Home Quilter are larger and reasonable for quilting. They are made in USA
Mary in TX

There are methods of quilting a completed top in sections. The one that pops into my mind is to cut the batting into thirds, lenthwise. You can leave the backing whole, or also do that in sections. basically, you sandwich the middle third, quilt to within about 2 " of the edge, join the next section of batting with a wide zigzag, secure the sandwich and quilt.
I'd be interested in seeing if you can find vinatage machine with a large harp. Maybe an older commercial Consew?