Hello, I bought my first big bike in 1971 at 14 yrs old. It was a 1968 DT1.  I started desert racing this bike in 72 and raced it until 74 when I bought my first Husqvarna.  I have gone full circle and am back on a DT1 for my trail bike.  I have a load of questions that I’m sure will come up.  First off is can a reed valve be installed on the DT1 or would I need to get a 74 or later top end?  Second is putting a 21" front wheel on the bike and installing a high fender?  I’m also looking for a rear rack for the bike.  Will a rack for a 175 fit? Or do I need to hunt high and low for a 250?  I hope you all don’t get tired of my questions. Thanks in advance. 
Charley

Greetings from Tennessee. 

Welcome Vikingson. A 72 and 73 top end will fit on your 70, that will get you a reed valve, a 74 and later top end will NOT fit. Yes you can put a 21 inch tire/rim with a high fender on your 70. The 70 MX had a 21 inch standard and the forks for the enduro and MX are the same.

Thank you. It’s been great reading up on my first big bike. Going from a Hodaka Super rat to the DT1 was a great eye opener for a kid. I won some good races on my DT1. Thanks again. 
charley

Welcome from NZ. Just a note, if you fit a "72 or "73 cylinder you need a conrod change due to gudgeon height difference between reed piston & earlier. 360 didn't have the same issue & could swap up to "73 without rod length change. Easy way would be to make a 5mm alloy base plate with a gasket each side & Job Done. Then you could easily swap back to original piston port top end if you wanted.
Re-thinking. If you want to go racing then a DT2MX top end would bolt on [with base plate or rod change]. Also a YZ250A & B, but good luck finding any of that stuff.

Thank you. I learned a long time ago that vintage parts, no matter what bike are scarce but occasionally can be found. Excellent information. I’m really glad I found you guys. Thanks again.