Is It possible to directly change a Canadian 300 in-line 6 to a In-line six ford falcon engine? truck has a 4 spd manual gearbox, wondering if it will bolt straight onto it?

 

What's a "Canadian 300?" I'm of the understanding that all 300 blocks were cast in Cleveland, but I could be wrong.

 

I'd imagine the engine mounts would be different. Bellhousing may work- looks like early 80's 200's (80-83?) will bolt to a smallblock (Windsor) bellhousing, and all 250-inch motors will. All the other small sixes (and the 250 through 1979) are the "Falcon Six" pattern.

But I'd doubt it'd be a direct bolt-in, mainly because of the engine mounts.

A small six would be interesting in a lightweight (F100, Bronco, etc..) with tall gears for around-town driving. But they're just not going to have the torque or breathing to do much in a big truck. What goals are you trying to achieve? The 300 is known for good MPG when tuned right.