Posted for "Ed Anderson" <eanderson@carolina.rr.com>:
John, the dimensions of the GM evaporator cores I use are 13 1/2 x 9 x 3
3/8" external dimensions.
Of the total coolant area,  approx 2/3 is for coolant and 1/3 for oil. The
rotary dumps approx 1/3 of its none-exhaust waste heat through the oil.

Ed Anderson