Doing an alternative engine install in the IH platforms will be a "from scratch" effort. There were never any "adapter" kits for these rigs as they were never popular amongst that crowd.
Also, the Scout 800 four cylinder chassis/engine mount/radiator/firewall doghouse, etc. Is considerably different in execution as compared to the Scout 800 originally equipped with a 266 or 304 sv motor.
Lots of difference in the offset of the crankshaft centerline as compared to the chassis centerline between the I-4 and sv versions also. Steering gears and columns are also different.
Can it be done? Sure! That's what hotrodding is all about! But it ain't gonna be a an ez "kit" kinda deal!