This is just a quick bit of info i came accross a little bit by accident really, i was putting straight (renthal) bars on my GSXR1000 K4 (see my other guide) but wanted to keep the original brake system all intact ie calipers lines and master cylinder all joined together to save time and hassle in the future if i went back to standard clip ons because putting renthal bars on means longer brake lines.
Anyway i bought a K5 GSXR 750 master cylinder which is a radial one unlike the K4 1000 although it has radial calipers, i put some braided lines back on which is what i took off and bought some second hand calipers with standard pads in, gave them a clean fastened them all together bled the system and went for a spin.
Even with the standard pads the transformation was unbelievable the radial master cylinder was the difference without question, the thing is you have a bleed nipple on the m/c itself to release any air in there unlike the old m/c so you can bleed the complete system. You see on a standard non radial master cylinder they have tendancy to gather air in them so when you squeeze the lever your squashing that first, a little like the standard brake hose effect with them being rubber they tend to expand slightly before the whole effort goes to the pads / discs.
Anyboby with an older bike should look at buying a newer RADIAL master cylinder to upgrade there brakes, they normally sell for about the £70 - £80 mark and will improve your brakes no end. I have just completed restoring a 1996 GSXR750 SRAD and that has had one fitted from a GSXR750 K6 and the brakes are now awsome.
All master cylinder's will interchange with other bikes as long as they are the standard 7/8ths (23mm i think)diameter fitting for the bars the only thing you will need to look out for is the thread pattern on the banjo bolts to the m/c there are only 2 types a fine (close together) thread or a course (wide) thread and once you know that just buy your brake lines and order the banjo's to suit.
Any question just get in touch.
Please vote if its been of any use to you.