what do i have to do to put a 1950 model flat head truck motor in my 1946 ford truck,it has flat head v-8 also,both are 1/2 ton.

 

Swap it in. I pulled a 51 merc V8 out of a '46 1.5 ton. As I recall - use the waterpumps on the 50 and you'll find issues with the water pipes: the 50 used smaller diameter hoses on top than the 59 series. Oil filter may have a few differences - your gauge might be actual pressure while the 50 uses an electrical sender. That's about all. Everything else is a match.