I am currently restoring/customizing a '72 620 for my wife.(By the way these trucks are REALLY hard to come by around here in Arkansas).  Anyway, I also found a '78 king cab in the woods that has the L20 motor. These motors look identical, where is the difference?  Is it in the head? And can I use the main bearings I scrounged up for the L16 in the L20 when I rebuild it? This may sound stupid to some of you, but I need to know before plowing into these motors.  By the way,... great forum, folks!

The L20 motor you have is actually about 3/4 of an inch taller than the L16, but should bolt to the transmission.  The extra height is in the block, to accomidate the longer stroke.  The rods are longer, also.  The L-20 has a larger main bearing diameter on the crankshaft.  So, new bearings.

Thanks for the info.   Is the L20 worth the swap? And are the heads the same, then?

It really depends on the condition of the motors.  All things being equal, the L-20 will have more power, but use more gas.  You have to decide what motor you want to use.  Years ago, I replaced the worn L-16 motor in my 1970 PL521 with a L-18, that was orginally fuel injected.  I removed the fuel injection, and replaced with the manifolds and carb that was orginally on the L-16.  I ran that truck for many years.  At that time, there was a large supply of motors imported from Japan, that came from fairly low milage cars.  The Japanese motors could be bought for a LOT less than the cost of parts to rebuild the orginal motor.

zacko where do you live in arkansas. i live close to russellville. drop me an email and i can tell you were to find a few trucks if you want to know.

mine is [url=mailto:[email protected]][email protected][/url]  any info is greatly appreciated.  I thought I found another '72 today, a friend said he saw the rear of one in a small salvage yard. After an hour drive it turned out to be a '72 Chevy Luv.     I do appreciate the engine info, though.  Very helpful!  I live in northeast AR,   Jonesboro to be exact.  Wish we had some swap meets near here!