ticking like a sewing machine

I bought my Duster in November, 2 days later tranny took a crap. it was replaced with a stock 904 (still chirps from 2nd to 3rd). the guy that i bought it from said it was mainly a race track car. on Craigs list ad said "Duster 360 MSD ignition, new duel flowmaster exhaust" plus other non engine stuff. i tried to get info out of him and he said he would track down his buddies friend who did the engine work. I got nothing from that. it has more than a stock cam as it idles rough but strong at 600 rpm in gear. the problem is that the engine ticks. most likely a lifter. you see i had the oil changed last week 15-45 Rotell and then an oil additive to help lubricate the upper cylinders. this was all fine for about 1 week on the oil change until i got on it on the straight away 1 mile from home. i drive it daily but want to be able to beat on it. what kind of lifters should i replace it with. also is there any way to ID the cam without removing it. i plan to pull the intake to get to the lifters if possible but dont want to tear the engine all the way down. THANKS