for a truck... that does a lot of towing... the swirl ports are fine, just be aware that their are small (~58cc) and large chamber(~64cc) chamber versions and if in doubt for something that will see heavy use lower compression will likely make you happier (I still tend to pick higher compression numbers than most and put a lot of effort into detonation control, I'd rather do extra work and get the extra MPG from the higher compression in most cases, but again, you're going to be unhappy if you end up with something that will only deal with a heavy load well on premium).
I have no idea what redeeming quality the 350 TPI heads have, I have at least 2 L98's sitting around and I doubt that I'll ever reuse the heads on them, they're just basically average smog era heads. OTOH, the 416's (used on 80's pre centerbolt performance engines like the L69, LU5 and LB9) and the 602's used on some 80s' 305 trucks and other things are actually probably my favorite traditional style production SBC heads, as long as what I'm building can deal with the small chambers (58 for the 416's, 52 for the 602's, though they both end up between 58-60cc after installing larger valves and some porting).
For the most part, smaller ports, valves, chambers... will make better bottom end and MPG, and the only one that will get you into trouble on a 350 will be if the chambers end up too small/compression too high. Bigger, better flowing stuff will make more power up top but is probably not what you're looking for.
Either way, I'd try to go spread bore 4bb if you're going carb... small primaries = good mpg and responsiveness down low, better than a 2bbl or a square bore, and the larger secondaries give you plenty of flow to make power up top if you want to.