Others have more experience on this than me, but I'd recommend adding an engine break-in additive with ZDDP to the oil, even if the break-in oil that you buy has it included. There are several on the market, just be sure to get one with ZDDP. I've used Lucas brand.
You might want to check the valve lash just to be sure that it has been set. To set them cold, I add .002 to the hot setting of the intake and .003 to the exhaust.
Be sure to follow the procedure outlined elsewhere in this forum to run in the cam as soon as you start it up. Basically, you start the engine and let it run for twenty minutes at 2000 to 2200 RPM. If the distributor has been set correctly for initial timing and the air/fuel mixture on the carb is at the initial setting (1.5 turns out from snug on a Rochester B), the engine should fire and run just fine for the cam run-in. After the cam is run-in, you can fine tune the timing and the carb.
After the initial start up, pull the rocker arm assembly and retorque the head bolts while the engine is still warm. Use the correct sequence as outlined in the shop manual. Back each bolt off 1/4 turn and retorque one at a time to 95 foot pounds. Don't loosen all of them and then retorque...loosen and retorque as one step, one at a time. Then put the rocker arm assembly back on and torque the six bolts at 25-30 pounds.
I started a rebuilt 261 this past Saturday (with Jerry's help from afar!), so it's fresh on my mind.
Good luck,
Matt
