to get 8 lug on your front axle, you will need to do 1 of 3 things: (best to worst, IMO)
1) everything knuckles out from a 8 lug chevy d44... knuckles, spindles, hubs, rotors, stub shaft, brake caliper & bracket, lockouts... the knuckles are stronger, and easier to get high steer, bigger brakes...
2) 3/4 ton caliper bracket, possibly caliper, hubs, rotors, & lockout (if not the same) from f250... to get high steer, youll need to get knuckles from 77-79 supercab or 76-79 F250... Ive heard the ford knuckles allow bigger u-joints & possibly Longfields, also bigger brakes
3) get 5x5.5 to 8x6.5 wheel spacers/adapters... these only come in 2 piece and will require constant checking, & not recommended for highway driving...
depending on the BS of the wheels, might require some grinding to clear 15" wheels...