Rear Master Cylinder reservoir screws ???

I'm trying to rebuild my rear master cylinder off my 77' KZ1000A. there's a plastic baffle inside the plastic reservoir at the bottom that covers 2 screws that hold the upper reservoir to the bottom master. Tried to remove the screws but can't even with an impact driver. In fact they started to strip out? Any suggestions?
The lower piston inside the master doesn't want to move freely, appears to be gunked up or rusted inside? Any suggestion on how to remove the piston?
If this master is beyond repair, what other rear master cylinders could you use other than an original one? Doesn't have to be stock for me as long as it works.

I used a new good quality long nosed vise grip pliers to remove the stripped screws , and clamped it in a vise.

Was the reservoir wet before you started ? if not soak it in brake fluid for a day or two first.

A little heat may also help if you are still having trouble.

JD

I sent you a PM but here's the message for all to share -
Mine were tight and I had to use an impact driver but they did come out ok.Sounds like someone may have used some form of threadlock at some stage...? Maybe use something to dissolve this - google "loctite dissolve" there's a few suggestions there. But there is a risk of damaging/dissolving the plastic reservoir! I have heard of another method - carefully apply heat to the heads of the screws with a soldering iron - this should soften the loctite or whatever locking agent and allow the screws to turn. Don't forget to replace the O-ring inside the ineer circumference of the m/cyl when you re-assemble it. Jim at Redline Cycles Skokie, Ill has 'em for $6-99, they're not the same profile as the original rectangular section seal but his replacement fits perfect and does the job!

(See my other post on the removal of your m/cyl piston)

Cheers,
Bill.