68 gmc 3500

[My Alter Ego]

Just become the new owner of a 68 GMC 1 ton flatbed and am curious about the interchangeability of suspension parts. The truck has 4 wheel drums and I would prefer to have front disc brakes and maintain the 8 lug pattern. I presume the 72 front discs would be a direct bolt on, but wonder if there are later models that would do so as well. Also, I would like to swap out the rearend and presume that 69-72 would also be a direct bolt on, but, again, wonder if there are later models that would do so as well. Any and all assistance would be greatly appreciated. Thanks in advance.