If you do it again, put the truck in 4th gear. It is stronger and a 'direct' connection, no reduction. Also the gear you should use whenever you are trying to 'bump start', FWIW.
There is no break-in of a cylinder head that I know of. Its parts don't need to get acquainted nearly as much as piston rings and cylinder walls which are supposed to form a moving seal.
You can use a garden hose to flush stuff out of the block via the water pump hole given it is removed. Unless you plopped stuff in the lower radiator hose, I would not worry about stuff in the radiator. You could flush the radiator given it is pretty much disconnected. I think I would use a hose, and try to push water backwards via the lower hose. Use some shop rags to seal the hose or nozzle and you should get a decent flow out the upper hose or radiator filler.
If the hoses are old and rock hard, it might be a good time to pop for some new heater hoses and upper/lower radiator hoses. I would also do the timing belt and the accessory drive belt(s) so you don't have to mess with stuff for a good long while. I assume you would install new spark plugs, or clean and gap the old ones if they are in decent condition. And last, new air and oil filters. I would suggest a rubber cam cover(rocker arm cover) gasket as the cork or cork-rubber gaskets seem to be totally dysfunctional. I have replaced several times, and never had one seal properly. I have a new rubber gasket on the shelf ready to install when I get a 'roundtoit'.
tom