Here is my solution. I'll be the first to admit it is overkill, but as an engineer, the tolerance was killing me. In one pic, you can see that the bolt circle of these pump flanges is not EXACTLY the same as the pulley. Its real darn close. I confirmed this on the tech drawings of each part. That is why the holes are oversized and the reason that spacing the bolts wont make it perfect. I'm sure it works and works well but I guess I'm just too anal. lol. This spacer was made by a local shop for me. The spacer centers in the hub of the pulley, and the spacer has a lip that centers inside the pump for machine perfect alignment. Took the shop about an hour to bang it out. I think he used a cnc but I'm not certain. Looking forward to the rest of the install. Gotta move my batteries first.
https://cimg6.ibsrv.net/gimg/www.off...fb139a61b5.jpg
https://cimg7.ibsrv.net/gimg/www.off...1705dba693.jpg
https://cimg8.ibsrv.net/gimg/www.off...bb8d0dd8f4.jpg
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First, cost to make? Will your machinist make more if asked?

Second, it looks like you have the smaller nipple going toward the balancer. On a big block, there’s a 3/4” hex head in the center of the pulley; how are you getting around the that?

The part wasn't trivial, but to me it was worth the $200. He said he would sell more. Since I'm pretty sure he did it on a CNC, he may have saved the file.

As for the bolt, I think it was a 5/8" bolt on mine and the bolt/washer fits inside the spacer and clears the pump just fine. Is that what you mean?

https://cimg7.ibsrv.net/gimg/www.off...d2bee8dc25.jpg

My balancer (Gen VI 502) is bolted on then the pulley is installed. The pulley only has the three bolts attaching it to the balancer. The way it aligns (which is good) would require the center to be removed to clear the bolt. Your balancer bolt should mount the same way (the washer seals the alignment key… dab of RTV… and spreads the clamping load of the bolt across the hub of the balancer). Your picture had the balancer bolt in the wrong position it seems.

Ah. Mine is different than yours. As you can see on the pic of just the pulley, there is a mark from the center bolt's washer. On my engine, the center bolt and the 3 other bolts hold this together. The pulley wont come off with the center bolt in place. I will need a new, slightly longer center bolt because now it bolts through the spacer and the pulley. The bolt/washer sit in an indentation in the spacer and will clamp it all together.

The hose from the power steering cooler to the old pump is larger. 1-1/2" I think. We now have 1-1/4 outlet from the pump. What sort of connector are we running to adapt the two? Obviously I'd prefer bronze but that doesn't seem to be available.

Has anyone tried this on an LS application?

My setup is 1-1/4 for the the entire system. I’ve seen adapters on many sites (Hardin, Jegs, Amazon, etc).

I think it can be adapted, but I know I read something about Volvo using this setup and having to move to a pulley driven setup to slow down the pump. Evidently, they have cavitation issues with the higher rpm that LS engines run at wot.

With that said, guys have been using this pump above 5k on big blocks and I plan to spin my 509s in the upper 5k range.

Yeah. I saw the adapters too but they're all aluminum I think. I don't think I'd want raw aluminum in salt in a spot that would sink the boat. Ideally bronze. Second 316 stainless. Are you saying that you run 1-1/4 directly to your PS cooler, or that the output of your old merc pump was also 1-1/4? I was originally going to run right up to the cooler with one hose, but the existing hose is quite complex and now I'm thinking I'll just connect where the old pump connected for the output. Input will be one hose from the seacock to the pump.