Best Upgrade for rearend???

[Ks Highboy]

I have a 67 F250 4x4. The spider gears went out and it has the 16 spline axle which parts are obsolete for. What rearend would be the best upgrade? I'm thinking 76-79 F250. If I could find a complete truck I would just swap in both front and rear diffs.

[cep62]

'77 1/2 -'79 will be wider by about 4 inches I don't know the spline count.

have you priced newer spiders and new axle shafts it might be more cost effective.

or weld your spides to the case and make it a locker.??