any benefit to swapping heads?

Small Block Chevy Intake, Carb, Camshaft Testing - Danger Mouse Part Four - Super Chevy Magazine 15 years ago
Test 12: Comp Cams Xe262h Cam
To either prove or disprove our theory on whether or not the engine needed more air to make more power we swapped in the next size larger COMP Cams XE262H Xtreme Energy camshaft (PN 12-238-2). The cam was 6 degrees bigger at 0.050 with 0.015-inch more lift and added a little more top-end power while giving away some low-end grunt.
It was kind of a wash, but we think the motor liked the XE256H cam better, and it would definitely have driven better on the street with the extra low-end power of the 256 cam.

Small Block Chevy Heads Test - Danger Mouse Part 5 - Super Chevy Magazine
And on a low-rpm street motor like DM, bigger is not better.
The large combustion chamber dropped Danger Mouse's compression ratio 1/2 point, putting it just below the 9:1 mark,
and the larger valve sizes, particularly on the intake side, probably reduced charge velocity enough to hamper the cylinder's filling at low speeds.
Note: Charge Velocity is a key

Small-Block Chevy Cam Test - Danger Mouse Part 7 - Super Chevy Magazine
Cam Trade-Off
We found the typical less-torque-for-more-horsepower trade-off when we switched to the next-size-larger COMP Cams Xtreme Energy camshaft.
Before installing it, we had figured that with only 6 degrees more duration at .050 and about .015-inch extra lift over the previous cam we'd ran, the XE268H camshaft would have worked well with the un-ported Vortec heads and dual-plane manifold.
However, after testing with the bigger cam, low-end torque fell off, and the only power gains were at the very top end of the scale (perhaps we should have run DM up higher with this cam).
Ironically, both peak torque and average torque and horsepower with both cams remained almost identical (see Test 18).
But it's low-end torque that moves a street car, and given the choice, we'd always choose the cam that could make higher vacuum and build as much as 13 more lb-ft of torque down low for our engines.
end quote
note: the UB Harold 1977 XE268H comp cam has about the same seat duration as the 260 Mopar Performance cam- The MP cam out torques the comp