Drop & Disc Brakes a few ?'s

[67-C10]

Alright I finally got most of the parts from the guy I bought my truck off of. Now the only item left is the spare 67 2wd SWB frame he's got. Thats no small feet in itself. This guys yard is like a junkyard of 50 to late 70 chevy's. So it gives me a little time to figure what i'm gonna do. I know I want to drop it and give it a nice level or slight incline stance maybe 1/2 in the back, in the end I want to put the same tire and wheel package all around maybe wider in the back but height wise the same all around, and disc brakes all around. I'm looking at ECE for the drop as the high recomendation from pretty much everyone. So i've always thought 4-6 drop but on occasions i wouldn't mind pulling a traier, (16 foot bass boat), would a 3.5-5 be more up my alley? Also from what i could find 71 up to 98 front disc brake 5 lugs are all 5 on 5 bolt pattern. I got a buddy with a garage that will get me anything at his cost and if I go with just the drop from ECE and i'm not sure but if the 2-1/2 drop spindles will accept 71 up disc setup i could probably save about $200-300 by getting the disc setup seperate. So any info if the ECE drop spindles will accept the 71 up to 98 disc setup?