Quite a restoration.
My 240sc is not in near as bad of shape but considering a full interior and more rebuild in the next year.
Don't want to clog this rebuild thread with a huge engine cooling debate but I have no problem running the motor on an engine flush. Mine has the Perko inline flush which makes winterizing and drive way running super easy. http://www.amazon.com/Perko-0456DP7-.../dp/B00144D86Y
I have never used the "fake a lake" plunger style but I don't think there is a problem there either. Just because it is not maximum flow does not mean there is not enough for sufficient cooling and lube of impellers. I have run mine for 10+min with no issue, you can watch the engine get warm, t-stats open then close with no problem.
Just a suggestion.
Do some research on marine sewing and upholstery, it is more specialized than auto.
Keep up the hard work.