Yes you still have to drill and tap you heads. You will also have to address the mating of the tails on your fountain. You have a split Y tail leading half to the transom and half to the bottom correct? The SM tails are designed to go to a rubber boot, making a big chore when adding to a fountain. Not to mention the plumbing for the staggered engine. If you choose the SM route they can custom build what you need to convert, but the price will go up.

Again, an improved CMI header that will be a direct replacement and utilize your existing tails is the best option IMO

I stand corrected, I thought I read somewhere that a place like Hardin was drilling the manifolds so they would bolt up but I guess not. On another note, it's not the corrosion that usually does in the CMI headers, it's the cracking, which there is nothing that can be done, that is just what happens to stainless after constant temp changes.

Here's what it boils down to:

Bling: CMI
Longevity/Warranty: SM
Sound: 50/50
Performance: 50/50

So it depends what the buyer wants, looks or ease of mind/trouble free boating.

I used the hardin hp500 system with installed bungs for efi , Easy install and have big sound !

the hardins are well built

After making some calls to CMI, Hardin and others based on all of your suggestions, it would appear that the CMI improved header is the best option for me. They are direct replacements, will work with my existing tailpipes and appear to be the most straightforward. All other options will require a lot more work and $$$.. Thank you all for your prompt replies and assistance. Greatly appreciated.

I'm with 302Sport. After cracking the CMI's 3 times and paying for 2 top end rebuilds I went with the SM manifolds. I am on my first season with them. Sound is the same, performance is the same. I had my guy paint them blue to match the 525 and I think they look pretty good. I'll upload a pic or 2 later.

What was the time period for which you cracked 3 CMI headers?

Port collector = 185 hours
Starboard collector = 200 hours
Port(near bottom, same header that went at 185 hours) = 220 hours

Basically ruined 2 of my last 3 seasons.

So roughly 35 hours of run time been through 3 headers and two top ends, sounds like fun.....

Ouch, that's brutal... were they the Gen-X headers?