We went through this with our 3588 about 25 years ago.  Was turned up maybe 20 hp or so, but was pulling it hard and EGT was over 1200.  We tried the different turbo, muffler eliminator, but did not get an improvement until putting on an intercooler.  That dropped the temp 100 to 150 degrees, iirc.

I agree with other posters, though.  I don't think the longevity on a 30 year old 2+2, pulling that load at that horsepower will be very good.  

Good luck, Dave.