i have a 350 and i put a set of stock 882 heads on it. anyways, once the engine reaches 5300 rpm's it starts skipping for just a second until 5500 and then it straightings out.
i havent had a lot of time to trouble shoot, thought maybe i would start here.

the engine is carbed with a few slight mods but nothing major.

 

I would check the endplay in the distributor. Remove the cap, grab the rotor, lift&twist. It shouldn't move more than 1/16" up and down.
If it's got a "bunch" of play (1/8") repair it.