A couple stupid questions!

[78cheyenne292]

1. will a master cylinder off other 80s or 90s trucks fit on my 78 and do i need one from a 3/4 ton being as my truck is 3/4 ton.. im not doing any towing or anything so can i get by with one from a 1/2 ton

2. were where the speakers originally mounted under the dash were they in the middle.. anyone have any cool ideas on were i can put two 5.25 inch speakers under the pad or anywere upfront.. pics would be nice

3. my gauge lights dont work they havnt since i got the truck and i cannot figure it out but the speakers someone mounted inbehind the switches and one night when i went to turn my wipers on my gauge cluster lit up and my wipers didnt work so i took the speaker out and everything went back to normal but i still couldnt get my light working.. does anyone have a pic of a cluster they could label the main power for the light or a wiring diagram for it all or any other info that might help me out..

thanks a bunch guys!!