2001 CR125 Engine question.

I just bought my son a 2001 CR125 as he is about to out grow his CR85. Have hasd the bike out the last 2 weekends and on Sunday, Engine quit. Kick start pedal had no compression. Got bike home and in garage yesterday and tore bike down.
Rod aparently came into contact with piston skirt and broke skirt into a 1000 pieces, and then the top of the piston hit the head on the exhaust side and slammed ring groove shut. I will tear down bottom end when time allows and inspect and see if it can be cleaned or if crank kit will be needed.
I have been all over ebay and some other sites looking for a complete 2001 CR125 with no luck, but have found many 2002-2005 cr125 engines. Will these fit into the 2001 frame? Thanks in advance
Bank of Dad..
P.S. Also looking for early to mid 2000 KX85 for other son, out grown his 65. Thanks again.

Guys, thanks for the replies, I talked with Eric last nite on the phone, and I decided to go ahead and send him the whole engine, so he can freshen up the bottom end and let him assemble the unit and ship it back.
But I still would like to know if the 2002-2004 cr125 engine will bolt into the 2001 Frame??? I want to buy a spare engine and have it gone through also, so its kept in the trailer and be ready if something like this happens agian...We travel alot and are all over the country all the time, so spares are mandatory.
Thanks again.