1990 SP Yellow/White block issue

[antonov225]

So, I have a 1990 Seadoo SP that I just picked up and am trying to restore. Replaced the starter, but ran into a really interesting problem when I went to put the exhaust manifold back on. It seems someone has swapped out the original yellow block for a white block (yet painted it yellow). However, when they did this, they kept the stock yellow exhaust manifold, which lacks the (what I assume to be) cooling passage. So, a couple questions.

1. Can I buy a white block manifold and install it on this ski?
2. If so, will the white manifold bolt to the yellow exhaust riser tube (not sure of the proper name)? The white block gaskets seem to have a larger opening for the cooling passage, but I'd like to avoid having to buy more parts than I have to
3. Are there any differences in hose routing that I need to be concerned with?

The previous owner also mentioned that the ski takes on water, but could that just be because the engine was spewing out coolant through the un-capped cooling passage?