ANYONE CHANGED OUT A 7AFE W/A USED ONE?, Blew an engine; thinking abt buying a Jap "used" one Options

[Rangemaster]

Son called one day, said he's stuck on the freeway. It seems he has a loud knocking sound coming from the engine.

After doing a leakdown check (#3 and #4 cylinders looks suspicious) we pulled the heads. Shop said valves and the top end were fine; head gasket was not blown either. Engines has 125K miles on it.

Upon cycling the pistons to TDC it seems we can push #4 DOWN about .020" at the start of the down stroke... this indicates piston pin or rod bearing problems.

Soooo... thinking 'bout removing the rest of the engine and installing one of the "used, inspected/tested" Japanese pulls out of Seattle that they ship over. They have a 1 year unlimited milage warranty and you use your existing manifolds/engine-mounted accessories. I plan on replacing the timing belt, water pump and thermostat in the "new" engine when I install it.

QUESTION - has anyone done a swap with one of the "used" engines? I'm pulling a 7AFE and replacing it with a 7AFE... don't want to go modding right now.

Can this engine be pulled OUT THE TOP? I've dropped the tranny before to do a clutch and hate working under the thing in the pit; it looks like if I finish pulling the accessories off and yank the water pump I might just have enuff room to unbolt the engine and slide it to the left to get the transmission input shaft out of the motor.

Any tips from someone who has been down this goat trail will be appreciated...