can you still put the bleeder blades in the old bear razorhead if you use a 75 grain steel broad head adapter like the one from three rivers?

I use the 100 grain steel inserts from 3 Rivers and I use the bleeder blades; but I have to modify the bleeders to fit over the adapter.  I use a dremmel tool and grind out the middle or meaty part of the bleeder so it can fit over the insert.  I grind it until it fits perfect where it locks in place.  If you grind out too much then it becomes too loose.  Works great for me.

can you replace the bleeder?

Yes, once you modify it to fit.  It's a great system.  It took me a couple of trys to get it right but once you figure out what needs to be done to the bleeder it's easy.