1987 mazda b2600, cracked head or block?

[Tristan]

Our of nowhere my truck started smoking white coolant smoke from the exhaust...ok blown head gasket.drove to the mechanic and it actually stopped smoking after driving for 5 minutes. Drove great and didnt perform any differently then usually. got the head gasket replaced, and the mechanic couldnt find any cracks in the head, but only checked by eye. After the head gasket was installed he claims that the truck now runs awful and still smokes, but every other or so times he srarts the truck it doesnt burn any coolant. He says the reason is the piston positioning when he starts it up. Sound like a cracked head or block??? 1987 mazda b2600 4x4 with 130k miles. Really dont want to let go of my old girl