Could you also wrap the exhaust pipes and muffler in a exhaust wrap to keep the radiant heat from the hot exhaust from soaking into the engine compartment.  This would keep the engine compartment temps down and might be enough to keep the engine cool enough.

Another Option:

Simply use the 2.1L exhaust rather than the 1.9L exhaust.  I have used a 2.1L on a 1.9 before with no boltup problems.  Then this would allow the use of the oil cooler with no exhaust clearence problems, then plumb in the lines.

If you have a bad exhaust buy the 2.1L.  If you buy the engine as a core, try to get the exhaust system also.

Use a sandwick plate to route oil to a small cooler (do not use a tube cooler causes too much of a pressure loss).

Robert