2nd gen brake boost 1st gen master cylinder.
 

Does anyone know if that combo will work or not? My booster is gone n I can get a new 2nd gen booster cheaper then a 1st gen booster. I know I'd have to drill two new bolt holes but that's not a big deal.

Many things to consider though. Interior side....Push rod length and travel. Mounting to your current pedal assembly. Then engine side...again push rod length, and adjustability, and bolt pattern of master cylinders, and casting bore size of the MC...will it fit into the 2nd gen booster?

I'd want to play with all these parts at the wreckers...or at least pay for cheap used pieces first.

You have some really good point here. I do know you can run 2nd gen hydro boost brakes so I figured the vacuum booster should go in the same way as the hydro booster would.

The vacuum booster does install in the same way the hydro does. However, if you have a IC truck, I don't know if the intake elbow will have enough room to clear the end of the MC. In the picture below, you can see how far it sticks out. You will need to enlarge the hole in the rod to 1/2". The brake pedal will also stick up quite a bit further than it did previously. Cutting out about 3/4" of the rod will help that tremendously. I still need to do that with my hydro booster. The good news is that the brake lines were a direct fit on mine - no adapters required.

https://sphotos-b.xx.fbcdn.net/hphot..._7657841_n.jpg