A big block is going to generate a lot of heat, so your cooling system needs to be able to handle it. You could install a 3 row factory radiator and maintain your factory fan and shroud, but I believe this would be marginal, and would have overheating problems. Another option is to install a 4 row radiator. Some '78-85 G-bodies came with diesel engines, these were equipped with 4 row radiators. You could go to the parts store and get a factory style replacement.
Here is source information provided to me: Radiator Express, the phone # is 1-866-723-3977. They have a radiator for a 1978 Malibu classic V8 5.7 liter, the radiator is a brand name and best of all it is a 4-row (26 X 17) for $182.95. You can also go to there website at www.radiatorexpress.com. Be sure specify that the radiator is for a Malibu classic.
If you want to use a stock fan and shroud setup, you will need to find a diesel G-body in a junkyard and get the fan shroud and supports (if you can find one!) I ended up going to the Chevy dealer to get the wider rubber "cushions" that the radiator rests on. I used brackets (that came with my electric fans) to secure the top of the radiator to the radiator support. I used electric fans with a built-in shroud (Flex-A-Lite 220 or 210). Works great and keeps the big block cool! See pic. 6 below:
View complete article @ Maliburacing.com
Purchase the radiator @ Radiatorexpress.com
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