how to convert 67-72 chevy c10 to 5 lug

can some one help me! i just bought this 1974 chevy c10 with tub rear and c notched with fenders cut out in front. 5x5 bolt pattern i am tryng to fit 22s in back and 20's in front. every rim place i call is telling me diff stories. is there an offset i should use? will 20x8.5 in front and 22x9.5 rear work? any help would be great!

mark did u order the 6 lug disc brake kit r do u know what kind of rotors and calipers i can get at the parts store

@one_low_sixty8 Just wanted to say thank you for the info more than a year later but Im working on a 68 c10 and I was wondering the same question Ive cross referenced the bearing and rotors the all matched up perfectly the calipers did not so easily but I made it work with slight modification thank you again