I recently rebuilded my DT75 -88.
Here is the parts I bought from Brownspoint, as said before $500 did it cost, one piston was scored.
Most but not all parts you need should have the same numbers.
After you have removed all parts from the powerhead you should bore/hone one or more cyl.
Dont know the cost in US, but I guess $150-300.
My biggest issue was the removal of the eight screws holding the powerhead-lower unit, they snapped one by one!
I heated the bolts but it barely helped.
Same with three bolts holding the cylinder head, they also snapped, but I could remove them with a large pipe wrench.
There is no big deal to assamble all the parts, but I recommend using a service manual.
Do you know why the piston blow?