I have 2 older 454 mags that need more (or I need more) power. I have been looking into 088 heads and then getting and edelbrock rpm air gap manifold with a Holley dbl. then I would like to get some aluminum manifolds and I all ready bought imco 4" risers.

Is this a good plan? Can anyone suggest better while taking into consideration some financial constraints? Am I better off running these and buying two 540 blocks and building them over time?

I know electronics exceedingly well, and I am not wrench shy one bit, but my knowledge of the engine isn't the greatest, but I am trying to learn.

Boat is a 1989 sonic 30SS. I have rebuilt so much on this boat why stop now. Shoulda done a resto thread

don't 365 hp motors already have square port iron heads? if so, i don't think there is much diff from one stock head to another.

I am no engine guy either but u did stay in a holiday inn select last night! I would say do a compression check in the motors. If good go with a new cam and a roller set up and get rid if the old flat tappet stuff. Refresh your current heads and do the rest of the stuff you spoke a about. That is likely the best bang for your buck. I just rebuilt my 454mags all stock and in retrospect I would have made these changes. Now - if you can save some money up I would leave these motors alone and look for some good low hour used ones on here that are pumping out more HP.

Would The size of the valves make a difference then?

You can build some decent power from what you have as long as they are healthy. I had great results from upgrading to a roller cam on my 420's which are very similar to your mags.

If they are 1989 454mags, then they could actually be 330hp's.

They are labeled 7.4 LX Magnum, 365HP.

I found some inexpensive aluminum rectangular port heads with similar dimensions to the iron 088 heads. Would it be a waste to buy them with the air gap manifold and holley's if I left the cam, lifters alone?

How would I be able to verify exactly what I have? Where r the casting numbers on the blocks? Where are they on the heads?

pull a valve cover. casting number will be between pairs of valves. do an ebay search for bbc heads. you will see pics of the casting numbers. i don't think block casting numbers mean a thing. they are same dimensions and material. (unless tall-deck or 502. but will tell you what gen.) and any casting number coulda been 2-bolt or 4-bolt. but if carb flange is down between valve covers, it is PROBABLY peanut head 330. if carb flange is about parallel with top of valve covers it is also PROBABLY 365 hp square port motor. alum heads are never a bad thing. at very least you are making back of boat lighter. plus iron heads rot thru after 25 years or so.

I tried my block and head numbers and they worked(mine where gen IV / mark IV too. The block numbers are on the back if the block on a flange just below the heads. http://www.castingnumbers.info/site/search/15445