If you want to just convert to 5 lug and keep the drum brakes you can get a 67,68,69 Corvair front hubs.
They are 5 lug 4 3/4″ and you do not need to replace the spindles. Now the rear is another item. Either send the axles out and weld the holes up and re-drill or purchase new 5 lug axles.
Disc brake are as described above.