Rear Caliper Piston disassembly plus brake Qs, 1971 914-4 Frankenstein Options

[mikesjunk]

Ok so Frankenstein is running and driving. Stopping well that was a different story. So I'm getting into the rear brakes first. Watched the awesome video by PMB Performance to get the know how. But my pistons aren't like those in the video. My pushrod won't drop into the adjuster hole so you can screw the internals out. I did try a piece of drill rod in the hole but the inside piece just spins. I see the obvious snap ring on here but want to know if it's a booby trap. I don't want to pull the pin and the piston sends its guts to all four corners of my shop. (IMG:style_emoticons/default/smile.gif) So what is the way to get the internal piece out of this piston?

(IMG:http://www.914world.com/bbs2/uploads_offsite/www.mikesjunk.com-19423-1459563369.1.jpg)

And the next question is can the rear prop valve keep fluid from getting to the rears? I have the calipers off and thought I'd see if I could get fresh fluid flowing. Pulled a vacuum on one side and it held. So jumped in the car and pumped the brakes and zero fluid coming out the open rear lines. I was able to take the line to the prop valve off and it flows brake fluid via gravity so I'm pretty sure it's getting to the valve. Thoughts on the blockage? I hope this doesn't have to come off as it looks like a real fun time with the engine in the car.