From John Tabor

some facts about heater cores
Four Seasons 94605 straight hose nipples, 2" thick core
GDI 399401- straight hose nipples, 2" core
GDI 399406 90* hose nipples 2.5" core
Everco H2357 90* hose nipples 2.5"core
the 399406 cores that have the 90 fitting which is the correct part for 
scouts, but all the books show the 94605 ,399401 as correct with straight 
nipples, [which is incorrect, since the 90* is necessary for clearance 
from w/washer res.]
the 399406/H2357 cores'tanks are to wide to fit into the heater box, 
because the core tanks wont fit into the end caps, unless the end caps for 
the core are widened.
so the coices for heater core replacement are get the straight nipple 2" 
cores and put some 90* fittings on /at the nipples for clearance, no kinks 
in hoses. or- what I did is= grab a extra heater box, take the core end 
caps from box bend them wider to accomodate the 1/2" wider core.
have to watch it though, because- seems the later heater boxes ['76+], the 
rear core cap was spot welded to the box, which will cause problems if you 
go to widen it.[cant remove it easily from box]
all the heater cores I ordered and inspected were this way- to wide,wrong 
nipples, no matter what brand.
so- there are the choices.

-Tom Mandera