Those heads would be OK for a mild 318 build. We just installed a pair of them on a 99 durango at work. They are made in China and it is very aparent when you see there quality in person. Actually the casting quality was horrible but the machining was good. They had smaller chamber than regular magnum heads but also smaller ports. As a matter of fact I CCd them while I had them to make sure my eyes were not fooling me. I also checked a couple other sets while I was at it and pulled out some numbers from previous stuff I did.

Head Brand, Chamber CC, In. Port cc, Ex. Port CC, In. Flow @.500

Factory Mag. 64 172 62 212/209 RyanJ/Hughes
Chinese 58 136 64
RHS Pro Topline 63 182 67
Edelbrock Mag. 58 176 75 249/231 RyanJ/hughes
Engine Quest 62 174 65 227 Hughes
R/T 63 239/247 RyanJ/Hughes
Mopar alum. 52

I will try to remember to CC my aluminum magnum ports this week.

The CCs are my findings and flow numbers are Intake @.500 lift and whos bench the flow is from is listed after them. I made them a nice chart when writing in the little box but it won't let me do it on the real screen

Been a while since I checked the R/T and I can not find the port sizes, mabey some one else has that info.

The chinese head a horible casting but for a very mild 318 the smaller chambers could help out, that was the only bonus I could find to running them, the 318 Durango didn't like them over 4000RPM. The R/Ts have rough castings but they look very polished next to the chinese ones. For a cheap set of heads the EQ is a better one and you can get them with a warranty for about the same price and you can get them with a LA intake bolt pattern so you can re-use your intake. The RHS is discontinued but they are super nice heads, I have a brand new pair I will sell for about what an EQ or the Chinese head would cost and I will put the LA intake pattern on if you want. PM me if interested. The R/T and Eddy mag are slightly better flow wise but a lot more $$$.