... the Carter 6270 will get high enough (6.9 to 8.1 psi) to require a regulator....The pump was always on the ragged edge of overfilling the fuel bowls and causing the carb to run rich and occassionally flood.
Exactly. The M6270 cuts off at too high of a pressure for most uses (w/o a regulator). Had the same issues myself. The M6902 is a generally a better choice.
On an LA with '69 and earlier water pump & timing cover, a 6 valve pump such as the P4529368 is one of the best choices.
With the Aluminum water pump, choices are more limited. I've had good success with the Holley 110 gph for small blocks, p/n 12-360-11.
Before landing on that choice, I sent three pumps to Ryan Brown (North of the border) who has a test rig for pressure and flow. If you have any questions or are circle track racing, you'll get a solid answer. Flow, pressure and fit details on this older page on fuel delivery on my website.