You're welcome I'm sure. I was asking those same questions about 6 years ago when I bought my '48 F1 with a flathead and got online service about the same time. Go ahead and ask away - I owe the brotherhood if you know what I mean!

If you're using the 8BA in your '46 you won't have any trouble. Make sure the block is clean - even go to the trouble of digging around in the waterjacket with wire. Make sure there is no left over scale or rust or casting sand left in your block. This is the single biggest problem in overheating.

Your radiator in a '46 truck is the same as in the late series trucks - I have a '46 rad in my shop and the only difference is the absence of a drain ****. Otherwise they're identical. The system holds nearly 5 gallons of coolant. Keep the coolant level about 2-3 inches below the cap - this gives the coolant room to expand in the top tank. When you do get it together, use 180* thermostats. Make sure the fins and core of the radiator is clean. Make sure your timing is correct and you shouldn't have any problems with it running hot.

I've put over 50,000 miles on my truck during the last 3.5 years driving from Montana to Ohio and Colorado to Canada - mostly in the mountains but also for 24 hours at a stretch across the plains. If you follow the above advice it should never overheat. Some of the car radiators are marginal, but the trucks have an extra capacity for abuse built in.