what are good spark plugs to run on a 340 and gapping ?

Hey everyone you guys have been a big help with helping me finish this restoration on a 68 dart gt that someone else started and I needed to finish .the car started out as a 273 and now has a 340 out of a 71 dart the last owner told me . when I got the car the electronic choke wasn't hooked up so you would have to pour gas down it . I hooked it up and my buddy changed the jets to 76 front and 88 back and 13.6:1 air to fuel since the guy had it running rich before( that's what the guy told me and I believe he had 76 jets in rear also ) . The car was running really nice all day Saturday and part of Sunday morning. It was low on gas so I put 15 in and drove home fine which was around the block and then I moved it 2 more times . then out of no where started running rough n felt like it had no power and wanted to stall.. I put the same gas in right after in my 71 mach 1 which is still running fine so I don't think it was the gas. I know the guy I bought it from said the plugs haven't been changed in 12 yrs so I figured I would new plugs and see if that helps since i 'm trying to sell the car . what is a good plug people are running with part number and gapping size? I just wanna run to auto zone and make sure they give me the right ones . the motor is a 340 with I think a small cam , headers ,msd blaster coil and i believe a holly 4150 single pump. thank you !