Hey Stewart,
You have a couple of McLaren blocks don't you? Those are different than the 6.1 Gen 3 aluminum blocks obviously.

If your main cap studs have the metric ends that go into the block and the 7/16 end that holds down the main cap, I'm thinking that the oil pick up stand off may work if you modify it with a 7/16-20 fine thread helicoil maybe?

Unfortunately the main studs on our 6.1 aluminum block looks like they are 7/16-14 coarse thread.

There is no way that is a fine thread. You can see the oil pick up stand off in the background.

I had forgotten to email Prefix until the last minute today haha I'm still out of town.
Awaiting their reply.