Modding block-only to full system close cooling
 

I've recently picked up a closed cooling system for a ridiculous cheap price but it's a block only system, and I'd like it to also cool my IMCO manifolds as well. The system is the typical BBC half system that everyone sells for around $800. I nabbed it for less than 1/3 of that from a local guy, so I jumped on the deal.....so....here's my question. Has anyone tried using this system to also cool the manifolds? The plumbing wouldn't be a problem. Adding a water neck spacer with outlets to the manifolds and bring that water back in via the spacer included in the kit (with a block off plate separating them obviously) would be simple. But I'm not sure the exchanger is going to handle the extra heat. The actual info available on the exchangers used in the kits is very sparse so I have no idea what kind of difference there is between the kits. And we have to keep in mind that my summer boating is done in water that sits in the high 80's for months, so that doesn't help the situation.

So, any suggestions or thoughts? Given the minimal $$ I have in the system I'm almost inclined to give it a try and if it fails it fails, but I figured I'd ask first!