These engines are tough as mother nature itself - I opened up one just for kicks - as the owner said - ring khatam hain oil use horaha hai aur socho 200,000 kms hogae hain - after opening it up and measuring everything - it was in perfect original spec including ring gaps except that the oil scraper ring had become blocked with grunge causing oil consumption, new hone job, new rings in place - lapped the valves and put back together, It ran perfect.. (my original remedy was to run some cleaning agent oil in it and install the missing thermostat valve for the engine to run normally warmed up and self clean itself)
The timing marks are kind of funny as the older 4K engines need a ruler to align the marks first then install the double row chain.
btw - spitfire why dont you paint the block with high temp industrial enamel - its about Rs 400/can and makes it look nice and new too (also prevents rusting) - and with such detail - you can also have every outer screw/bolt/nut galvanised - it will make it look like a factory fresh engine.
btw what fan are you using on this engine? I always throw away the silly fixed plastic fan and install a clutch fan - much more quieter in running and more effecient cooling once the fan clutches at normal engine temp; and it also saves the water pump from dying an early life