Another one of the main fabrication
hurdles with the swap (but one of the easiest and funnest!)
is routing the coolant system lines. Luckily, the input &
output of the water system is on the exhaust side of the engine.
Instead of trying to find rubber hose of the exact shape,
I purchased some 1-1/4" 0D 6061 Aluminum pipe from a
local supplier for the straight runs. It was cheap and very
easy to work with.
The engine-radiator line was easy to fabricate. If you notice
closely I reused a line from the 16V engine as well as one
from the 20V clip.
The radiator-engine line was more complicated since I needed
to incorporate the filler neck. Also, I am not using the stock
MR2 oil cooler, so I don't need to route the line over the
exhaust manifold. (if you do use the oil cooler, just mount
the filler neck over the manifold.) I ran the line over to
the driver's side of the car, straight up to near the fuse
box and then back over into the thermostat housing. For the
elbows I just purchased 2 proper sized hoses that each had
two 90 degree bends. Then just made up some brackets to hold
the pipe to the firewall. I attached the filler neck to the
firewall as well.
The heater core lines are a lot easier since you just use
flexible rubber hose. I forget the diameter I used, but it's
the same as the 16V lines. I used the same bracket that was
on the tranny to hold the lines in place. You can sorta make
them out in the below pic: