Need help with my new cam

[78' Silverado]

Ok, well i went to go look at cams today and ordered on lol. Its a Pro Comp .268 Cam. I have talked with alot of people and they say its to low, the guy who i talked with said it would be great cuz i am a daily driver but love to race alot. I dunno.....Some people said i need to get a cam in the .4 range atleast lol. My engine is a 4 Barrell Goodwrench 350 96' i think, Its got a full flowmaster exhaust with 2 muffs, with new Flowtech Headers. I dunno if my .268 will work good with it or if i need to sell it and get a cam in the .4 range or something lol. I do kow one thig though I will from now on reseach any part that I wanna buy, so i actually know wat i am getting, and that if i could get something better for the same pirce i know wwat that is lol. ANyways any help would be great you guys Thanks alot!!

Tyler