Tell me why not?

All,
I want to wake up my '75 Smog 318. I already have 2.5" TTI haust with 340 manifolds, 904 trans, 3.55 sure grip 8/1/4. Looking for more horses with some street manners. And please don't tell me to buy a 360! Thanks in advance, I know nothing about engines, cams, air flow, etc. but I'm trying to learn. Also, someone told me to go with roller rockers and a roller cam if I do upgrades?
Speedmaster PCE281.2149K: Small Block Chrysler Cylinder Head Kit | JEGS

Tell me all the reasons I shouldn't buy this? Plus you get $100 off $1500 or more, and free shipping, this looks like a deal to me?