My mill has an R8 spindle, too, and it is very tedious to have to knock a collet loose, remove it, replace it and tighten it up just to switch tools. This led me to the Tormach TTS system that uses a modified R8 collet to mount tools. You simply loosen the drawbar and tap it to release the tool, then insert the next one and go. Very fast and they offer a boring adapter to fit the better boring heads. Any 3/4" diameter shank will also fit into this collet and speeds things up considerably. You might want to take a look at the Tormach tool holder system but you can do the same thing with any collet. Just use the same size shank of your most commonly used tools.
With regard to boring heads, I prefer Criterion heads. They are well made, precise and direct reading. That is, what you dial in is what you get. The DBL series from Criterion is probably the most widely cloned design on the market for a very good reason - it works. My oldest Criterion head must be about 30 years old by now and it still works as well as the day I bought it so they're a good value. There are many higher end heads, boring and facing heads and even heads that can work in tenths but for the average hobby guy, a standard Criterion DBL-style head will work for the vast majority of your projects. I also think that a 2" head is sufficient for most of us; it will go from tiny out to over 6". These smaller heads usually hold either 1/2" or 3/8" diameter boring bar shanks and while I have heads that use each size, I prefer the 3/8" bars because of the reduced mass. Lower mass reduces centripetal forces so vibration is likewise lowered.
Look up the Criterion DBL-202 boring head on ebay. The 202-A holds 3/8" bars, the 202-B takes 1/2" shanks. If you are patient, you can find a head in good condition for a fair price. All DBL heads are threaded with a 7/8-20 back and adapters to fit any machine are available.
