Replacing an entire spindle

Hello,

I have been considering replacing the quill/spindle on one of my Bridgeports for some time. The objective is to be able to use BT or CAT tooling, and to be able to run much higher spindle speeds.

I have been looking at various spindles on Ebay and elsewhere, but frankly they all seem to be the same unit(s) sold by different sellers.

Most are BT30, and some boast 10K speeds. They are usually referred to by their max input horsepower. There is, of course, no documentation which fully describes their construction or performance.

I have already addressed the Z motion and have made adapter plates to accommodate a new housing.

I have wrestled with buying a block of cast iron (like DuraBar) and just making one, but if I can get one pre-made I would prefer it.

Does anyone have experience with any of the machining spindles sold on Ebay? (Not the ones for routers)

Why not install a BT30 Bridgeport quill? I have one on my machine. I think the R-8 and BT 30 spindles are interchangable.

I have considered that before, but I wanted to also have higher speeds.