My first impression was that it looked early 60's Ranchero-like from the pic but bulky up top. Raising it a bit will help as suggested to get it more truck-like and bumper to lengthen bobbed back. The breakup suggestions I don't know about, the length between wheel wells doesn't bother me too much as uni's tend to look long in the body.
Funny, I have always thought the long bed unibodies had too much overhang, and that the shorties looked just a little too short, making the roof appear a bit tall. And what has been done to this truck is something I've pondered over for a while. Looks seriously great, and just different enough to make one wonder exactly what was done. (which is what I wondered when you had a pic on the "what color should the trim be" thread.) PS leave the side trim off. JMHO.
I can't make any comment for or against the proportions but you IMHO you couldn't pick a better set of wheels. HRP