rear ends, back spacing, and wheels

[bugmasta]

ok guys, i have spent 3 days reading and researching the best i can so please don't flame me and tell me to go do a search. i just want to confirm what i have been reading and get direct input. here is what i have:

1968 C20 LWB with a 1972 c10 rearend and c10 conversion drop spindles on the front.

front end has 72 rotors and the rear has 72 drums.

i want to use Boss 338 wheels and i know there are issues with the fronts.

i am considering 20x8.5 fronts with 4.5 back spacing and then 20x10 rears with 5.25 back spacing.

these are my questions:

will this work?
will i have to grind the front hubs?
will the tires rub the rear?

currently running 17" wheels and want something to fill the wells better. here is a quick pic as we were loading it to head to the glass shop: