Ive got a bone stock carb'd Gen 5 454 Mag. I have found a set of oval port heads off a early 90s GM truck. Since Iam sending my heads off next week to get freshend up, im thinking about sending the oval ports off instead of my rectangle ports. Iv heard that these oval ports will add around 20 or more HP since they increase the port velocity. With the addition of an oval port intake, would there be anything else I would need as far as valve train? like any particular springs, valves....etc?

Most likly those are small (peanut) port heads. I use large ovals and are bigger. If you change the heads you will have to change the intake. Also Gen V or VI heads should not be used on the Mark IV block. However Mark IV heads can be used on a Gen V block. Check the casting numbers and look at Mortec.com that will tell you what you have.

WRONG,dont do it,the peanut port head is way to small for marine use.if you install those heads,you will loose power above 3000 rpm,it will be a DOG.

yes, those heads are junk for power, you would need casting 781 they work great and make great power to 6500 and some cases will make more power than the rect ports when done right...

049's are ok too

I use the 820's, I went with them because they have a smaller chamber. I have flat tops -3cc, 110cc chambers, 489ci for 8.9 to 1 comp.