power brake booster push rod adjustment tips anyone?

I just upgraded to a rebuilt brake booster and master cylinder. The master cylinder came with a spacer that allows the booster to ventilate. It seems like a good part to use. Anyways, that spacer sets the master cylinder about a 1/4" more forward and really is stretching the amount of usable threads on the push rod adjustment. Current pedal travel is about 1/2" before push rod engages the master cylinder. Is there a location that I can buy a longer threaded acorn piece? Is there a travel spec for the car in my signature?

I don't see much of a better way than to use trial and error in setting the push rod distance. Do I need the engine running to maintain vacuum on the booster? Thanks for your help!

Why would you want to ventilate the master?They have been bolted to the booster for 60 years.I set the rod so its about 1/16 inch from the piston.My kids 300 has been on for 15 years and no problems even with big tube headers.Rocky

if you find a way to extend the rod, what I did was look into the master cylinder as I push it onto the booster.

there is a hole at the bottom where you can see the piston.

I just watched it as I pushed it flush. I extended the adjustment out enough that I could see the piston move, then backed it off till it didn't move any more when I pushed the master on flush.

Had these instructions in my reman booster.....