*If* I was going to give Abx post endo (and that's a big if since in theory before you obturate you've debrided, shaped and disinfected the root canal system), in non pen allergic patients, I'd give Augmentin 875mg tab BID x 5 days, and for pen allergic patients, a Z pack.
Reason why I don't just give Pen Vee K, plain and simple, my local endodontist Rx's Augmentin or a Z pack as he's managing his cases and in theory atleast, my treatment is held to the level of his treatment, AND IMHO more importantly, the Augmentin and Z-pack require both a lower number of days dosing and a lower number of times per day dosing, thus increasing the chances of full patient compliance