If by "fit in my truck" you mean "bolt in", then newest is 1972. I think 68-72 are 5 lug. The 30 spline would be a stronger rear than 14 spline, but if you're not beating on it you may never need that extra strength. Are you building a street truck or a drag racer? Gear ratio availability is more relevant I think, but a 3.73 with a 700r4 Sould work nice with a 28 to 30 inch tire height. If you're doing a 5 lug axle swap, just be careful with wheel backspacing. According to Lolife99 in the "track width" thread I started,
http://67-72chevytrucks.com/vboard/s...83#post3595683 ,the 73-87 axles are 3/4 of an inch wider.
Ralph