I am building an s-10 too. I had a 406 that made 587hp @6700 rpm, that went 9.94 @ 135 in a 65 elco that weighed 2800lbs. My 406 had almost everthing that yours has. My cam was a Ultradyne 279int 281exh @.050 and 630 lift, 13.5-1 comp, Victor Jr. Demon 1050, 1-7/8 2" step, 1.5 rocker, AFR210 fullport. It made it's most power @ 38 degree, @ 36 it made 584, @ 6500.
I blew that motor up and went to a 434sbc. with all the same valvetrain. It made 602hp @ 6300rpm, and 559lbs @5000rpm @ 33 degrees timing. I dynoed it with 2 sets of headers.... the 602 came from a set of 1-7/8 step 2" with 28" primairies, I switched out the headers to the HedmanHustler S-10 fenderwell 2" primairies, and 24 long primaires. It lost 50lbs and lost about 15hp. This motor needs 28" primaires tubes, and a nice collector.
Your motor probably needs a good header and a better carb, leave the 4.10's. I am running 4.10 in my truck. Try 34degrees of timing and go up or down 1 degree. You should be running around 125-130mph.