1972 307 cam selection... HELP!

[SpicedIcePirate]

Hey all,

I have a 1972 C10 longbed with a 307 in it.
I used to daily drive this truck, then it sat for two years, and now I'm wanting to keep the original engine but make bit more power from it.

Current specs are:
307, newer 4bbl intake from a junkyard and a 4bbl Rochester Quadra-jet I got for free off a 350 and rebuilt. HEI distributor. Full 2 1/4 inch true dual exhaust with (now burnt out) glasspacks.

This is backed by a rebuilt 700r4 trans running a stock converter. 3.07 rear gear, open diff.

255/70/15 tires.

I've helped plenty of people move using this truck, and hauled many things. It'll cruise at 60-75 all day depending on how many hills and how steep they are. I like the reliability of this setup, but I'd like a bit (or a lot) more pep at cruising speed and low/mid rpms. I know the 307 will never love winding to the moon and will never be a race truck. Though I hasve beat on it and suprised a few people at redlights when it was a daily.
I would consider changing to a 3.73 gear when I have the rear end rebuilt to be a posi. So consider that in the response.

I have access to some good heads that are casting number 3998991 that came off a pretty strong pulling mild 327 a guy had changed out for a 350.
These heads are free and I can use them if they'd be better than the stock 72 307 heads.

I know I'll likely need to get headers and potentially step up my exhaust size to 2 1/2 inch to take advantage of a more aggressive cam.

This is not currently my daily driver, so I do not care about MPG beyond interstate cruising. It'd be nice to get more than 14 running 75mph through a full tank though. That's my current with the 700r4. I feel more low/mid rpm power would make this happen just because it wouldn't find the need to downshift as often on longer hills.

So, with these current options, what would the best combination be for low/mid range power, redlight to redlight fun and cruising. I feel like I've fallen victim to the 'soft cam' issue of the era.
Otherwise I'd rush in with the 5.3 I have sitting in the corner of the shop, but I'm trying to convince myself to put that in an 84 S10 I got as a bonus when I bought my house.

Thank you all in advance, I've done a lot of reading online, but most people are all "I wanna make my 307 as fast as a 350 with the same mods".

tldr; With my current setup, what cam/lifter kit would I gain the most benefits from in a usable power range. With the addition of other potential bolt-ons (eg. exhaust).