no one suggesting the s-10 frame??? the crescent wrench of frames, one size fits all
the best frame for your truck is the stock frame. a mustII x-member and a flipped axle in back on stock springs will ride well. a c-notch and minus a few of the heavier spring leaves will smooth out the ride a bit.
box the full length to stiffen the frame a bit. for rear end choices go to chevytrucks.org
scroll way down and you will see options.
martinsr and new interiors need to calm down a bit and take their meds...