Hey folks,
I recently picked up a '74 DT250 to have as a spare parts bike, but it's almost nice enough to put the work in to get it back on the trail. One problem is that the front end is pretty crooked. Triple trees are bent, and the forks desperately need a rebuild. Rather than finding replacement front end components, I thought it might be fun to swap in a better/more modern front end, and throw some better rear shocks at it too. I found a list of front ends with matching bearing sizes, but it doesn't account for stem length. I have a buddy who can help me out with machining if necessary, however I want to first see if anyone else has done a similar swap and has any direct fit recommendations.

Thanks!!

As has been discussed here several times, the problem is "modern" stuff is usually leading axle and your bike isn't.  You'll have to dent the the snot out of the gas tank to get turning clearance since the leading axle triple clamps have much less offset to get the geometry right. 

As far as stem length, Yamaha kept the same bearings and stem length for literally decades so it's not hard to find a set of triples that bolt on.  Gauge and headlight mounts did change. 

Triples will bend back easy enough when bent from twisting.
Just loosen the clamps enough to move only, then twist back a little more than need [via the handlebars] to get past the stress point & then bring back to the center & it'll stay there--then tighten up.
Ok not quite that easy but can be done in-place without major surgery.
But that is providing the tubes [stanchions] are straight, so you don't get a false indication of twist.
Anyway--that's not helping sorry.
You might find any DT250/400 forks up to "78 will fit, so a few options there & probably with improved internals.
I have what i think are "77 forks in my "72 360 bitsa bike.
Handlebar clamps are set back a little & angles upwards.
Top clamp is alloy but not sure on lower one.
Steering stops might not line up the same.

Might see the bars set back in this pic although could come up too small.
photos.app.goo.gl/xYXDNjDA8BN9GEec7

Hey RT325 getting a error 404 when trying to open your link

Try 'that' now. Forgot how to link it lol. Nothing flash to see.

Also, you can always use RaceTech emulators in the forks... MikesXS used to have "knockoff" versions a lot cheaper. Not sure if they still do.

I fitted 76 IT 400 front suspension to my 74 DT, the it forks have a little over 8 in of travel and are 36 mm instead of 34 and use alu triple trees, a little creativity is needed to fit the original gauges and headlight ears.