You'll probably wind up replacing some of the components, but even then, they are still a great bargain.
The coupling caps are tubular poly.
The transformers are low-end Asian manufacture.
The tubes are Shuguang.
I'm using them to build amps for clients, and I find it necessary to replace the knobs, switches, input jack, pilot light, and most of the tubes.
The way I would go about it as an individual, making an amp for my own use, would be to first build one of these "stock," then if I thought it could be improved upon, swap in different components and see what happens.