the 18 heads are not the same as 21 heads .
You can have your 300 barrels machined at your local machine shop . All you need is the measurements .
You need barrels , heads , 150 base gaskets , head gaskets , tyga powervalve cables , tyga special hose for top head , tyga exhaust flanges . The standard 150 powervalve pulleys . Tyga pistons , I hope i have not forgotten anything .