The long bolt taper is there by design .... it is used to allow proper rocker oil flow in the oil passage hole. Chevy's and JD's do not have this 'feature'. And the taper is not the weak point anyway: the minor thread diameter is smaller and is a stress riser shape so that is the weakest point on all the bolts, tapered or not.
BTW, I don't think it'll blow up if you used standard grade 8 bolts. In your shoes, and if all I wanted to do was move the truck around, I'd assemble it with them for now IF they fit right, and then put in the OEM ones later. If this is a stock engine, I'd be willing pull them out one at a time later and replace.
1) Just measure the head depth at the head bolts and check that the grade 8 store bolts have thread far enough up the shank so that the end of the unthreaded shank is at least 1/8" above the bottom of the head when inserted, so the end of the threads doesn't jam down into the block and give you a false reading of being torqued properly. Typical graded fasteners only have 1" of threading.
2) Look at the head sizes and make sure they don't goof up the bosses in the tops of the heads; they may be too big. If you need flat washers, SAE sized ones are narrower.
3) Be aware that a long bolt with an untapered shank is going to reduce flow to the rockers somewhat. YMMV
