Yeah the rear radiator always seems sketchy to me but it seems to work. There is lots of drag week guys that do that. There is a guy in particular that daily drives his 7 second mustang in Dallas traffic, he just recently added AC and put the condenser stacked with the radiator under the trunk. As long as you have a mild engine that doesn't make any heat under normal driving conditions it seems to work. Like I said though, on MY car, I bet it'd run hot real quick. My old school stuff isn't quite as efficient as the new gizmos, lol.  Newer design mild engine w/ a big power adder is def. the way to go for a street driven car that's gonna see a lot of miles. I like doing things the hard way I guess, w/ old school stuff in a heavy sled...but it's what I like. 
CHIP
'70 hemicuda, 575" Hemi, 727, Dana 60
'69 road runner, 440-6, 18 spline 4 speed, Dana 60
'71 Demon, 340, low gear 904, 8.75
'73 Chrysler New Yorker, 440, 727, 8.75
'90 Chevy 454SS Silverado, 476" BBC, TH400, 14 bolt
'06 GMC 2500HD LBZ Duramax
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