MT 2 tail stock tooling is easy, since so many other lathes use that same taper. Although I’d very much suggest that buying on price alone usually doesn’t work out well. The same for any cutting or knurling tools. Knurl wheel quality is 100% related to the quality of the knurls it will produce. Poorly formed knurls of low quality can not produce good quality knurling on any material.
The traveling steady would be a bit tougher, if you want directly fitting, then the correct Emco part would obviously need to be found on the used market, and it probably won’t be cheap. Adapting one from a similar sized lathe might be possible, but it depends on how your lathe was designed to bolt the original in place and how any other brand of lathe did the same.
Without already having a separate mill, then yes the 6 spd rear mounted mill would be highly desirable. But any mill is just about useless without the additional tooling. The correct direct mount collet chuck and collets, as well as either a OEM vise or one that’s sized well enough to still be clamped to the tee slotted cross slide would be the minimum. Again any of the original Emco items are likely going to be tough to source and expensive. I’d also want a correctly sized clamping kit with tee nuts, bolts, studs step blocks etc. But there’s generic kits of those that should fit. My memory is a bit hazy for what spindle mount those milling heads used. And afaik, Emco didn’t sell any low quality ER collets for there mills, mine are made by Schaublin and were expensive. But the run out numbers match the price. If I recall correctly, I believe Emco used ER 25 series collets on those mills. For whatever reason, Schablin seemed to use the prefix ESX for there own ER 25 collets. But the dimension’s are exactly the same.
Finding a tooling “bundle” with the correct sized tooling to fit your Emco might be doubtful. Other than finding original Emco accessories, your in the same position as anyone buying what you have when the machines were brand new. Any additional tooling is always directly linked to what type and size of projects your doing.