His issue with the crank bearings is that the cranks are different.
His dad is the brains here, he's clearly an engineer of some kind and its only an engine, they are not as complicated as you might think, you just have to be methodical.
The worst bit is the parts, the conrod cap bolts are stretch and use only one and something silly like £25 each (x16), you start adding up the parts and a salvage engine works out the cheaper route. Also, when the engine locks it bends the Conrad and cracks the liner which are sold as a pair, piston, liner, bolts and rings at about a grand each.
We did Loz's GS engine and there were no rings available so we were forced to buy the complete piston and liner set.