Once the pistons are out ,crank removed, valves removed from the head, take block, head, crank to a friendly engine reconditioning place to get them to..
Measure bore wear.
Measure crank wear.
Inspect head.
Worse case is rebore which means all new pistons or even worse, liners need fitting.
Crank may need a grind with oversize shell bearings.
Head might be cracked( they can test for that) valve seats might need replacing ( worth doing anyway for unleaded petrol) new valves too.
Get them to quote for these jobs then price up the pistons/shells etc yourself and decide what to do from there.
That engine is simple to assemble correctly with help from us on here and a Haynes manual.