The Edelbrock performer RPM package is a clone of the RA1V system. The heads are an aluminum version, which 72 cc heads should not be a problem with your 400 as they are aluminum. The cam is also the RA1V cam. The RPM intake is different as it has longer runners, it is an inch taller than a stock intake and gives you more top end with higher rpm. You may want to look around other shops before going to edelbrock.
www.krepower.com is one.KRE has an aluminum D port head that is a newer design and is supposed to be great. They also sell edelbrock heads. These KRE heads are new technology and they could also advise you on a newer technology cam etc. The RA1V stuff was developed 36 or more years ago, though great back then, today there is better products. Also once you get your engine apart you may need to do some machining and since you will be in there, why not upgrade the bottom end?