Ok, so my 351w is acting up i just rebuilt it and when I run the motor the engine overheats but it does it in cycles..(heats up then cools down then heats up then cools down..etc..) it does it fairly quickly, the radiator was 40% clogged so I replaced it entirely and I also put in a new thermostat (yes its in correctly)..I'm kinda stumped here all I have left is the water pump and the guage in the truck.... or maybe there is a blockage in the motor?(however when I took the heads off it didn't look all that bad)

my motor is also bogging down under acceleration it idles just fine but when you try to accelerate it pops and boggs down, I've replaced my map sensor and still no change

 

coolent might have a air lock, maybe take a few runs to get the air out .
check the vaccum lines all over the engine. plus did you crack the distrib cap? check leads . fuel filter?