My 10 year old son rides a 2007 CRF70.  He is about 4' 6" tall and about weighs about 75lbs with gear etc.  We mostly ride desert/trail.  He is getting to the point that a bigger bike may be needed soon.  I am not sold on going the two stroke route.  He has raced some desert style races in the past but it is not something we do often.  The next bike I am looking at is the CRF80.  He is too short for that at this point and it weighs a lot for him right now.  So I am thinking about modifying a few things on his CRF70 to help for some growth.  I have several questions.  

1.  I am thinking about getting a longer shock or a shock extender for the rear to raise the seat height a couple of inches.  I don't know what size/length to look at.  I had cut the seat for the past couple of years to help because he was short.  That was a huge help.  I put the foam back in that was removed to make it back to normal seat height.  He can just flat foot the bike with all stock settings.  I am not looking at making this a highly modified bike.  I have two other boys that I will go back and forth with the sizes as they grow up behind.  What are your thoughts on either of these products:
Shock Extender:
http://www.ebay.com/...#ht_2201wt_1413
Longer Shock:
http://cgi.ebay.com/...#ht_3484wt_1314

2.  If I raise the back by 1-2" will I need to do anything to the front forks?  If so, what do you recommend?  CRF80 forks?  If CRF80 will I need the CRF80 Triple Clamps or just put the CRF80 forks into the CRF70 Triple Clamp?  Any thing else to consider?

3.  I have the option of buying a 1997 KX60 for under $400.  I know I said that I was not interested in the 2-stroke option but for that price would it be a better option than trying to raise the CRF70?  For under $100 easy I could raise the CRF70 back end but not sure about the front costs if any.  Thoughts?

Bottom line:  I am thinking of raising the back end for a relatively cheap mod and then holding out for a CRF80 in about 6-9 months or longer if he doesn't grow much.  

Thanks for the help and info.

well a China shock (IMO) is not the way to go...usually one that will fit is too springy....not really the way you want to go financially but what I have found the best shock (adjustability wise) Is the Fox Float.....but they are about $300....dang good shock tho.....IDK about them shock extenders...they seem to be a weak point for me but if other peeps have used them I wish they would chime in....as far as your forks are concerned, the CRF70 fork is what BBR used to design the SP-5 fork...so if you put stiffer springs and BBR emulators (if you can find them, I have heard they are the same as XR80 tho...the BBR springs are scarce too but T3 sells some)..the emulators will give a little more travel and better dampening and the springs help in the bottoming department....I found that for my daughters bike and her SP-5s I had to use one BBR spring and one OEM CRF70 spring because she was not heavy enough...hope this helps or gives you other ideas....mounting CRF/XR80 forks on your 70 will make the bike way choppered...you will need a longer swingarm or cut the forks down (expensive)