This is very easy swap, only 3 things normally need attention, water pump,throttle linkage and exhaust. You need to shorten the water pump about 2 inches. Unless you have the right pulley and a press, just buy one ready to bolt on . The 235 pump works just fine on a 261, same impeller, and 4 lbs cap is ok. You may want to bolt the 216 thermostat housing and hose neck on the 261 for an easier upper hose hook up.The engine will bolt right up to the 216 clutch housing, use the original 216 flywheel if you are keeping the 6 volt starter.The stock 216 clutch will be ok if you're not doing burn outs or pulling dead FoMoCo's around. I use a later 164 tooth flywheel and 10.4 inch clutches on both my trucks along with 12 volt starters. 261 original flywheels were the heavy duty 11 inch clutch with 9 bolt pressure plate.The flywheel has to come off to remove the clutch housing.You may have to fiddle around with the accelerator linkage, as the hole for the block mounted bellcrank is in a different place.On our 261 powered 51 truck,the original style full flow filter mounted on the intake is a hassle to change the filter.Same style filter and can as early Chevy V-8's.Gonna change it over to a spin on filter head mounted low on the block like my 37 truck.Of course your exhaust may need some reworking depending on what you have for pipes right now.The 261 is not as smooth of an engine as a good running 216.Its best to change all the motor mounts while the engine is out.Try to buy USA made rear mounts. The imported mounts failed quickly on my 37.Have fun and don't lose the headbolts
