Hi, not sure if this hyelps but going by the drawing it looks like "flat across the base & tapering at the top. Cheers. 

Thanks RT , I Googled several images of 74 dt250a and have a good idea how the bracket goes now, and after reading around on the forum about grounding things , I think I'll carefully grind or sand the powdercoat at the handlebar clamp , coil mount, , I guess anywhere the ele. diagram shows a ground. I'm a little foggy when it comes to reading electrical diagrams never really learned how . tommorow I'll put the acid in the tiny battery and try to get the horn and signals to work. I've done so much reading about this DT my eyes and brain hurt.
Thanks again
John

It's a pitty to have to grind off powdercoating. If the loom earths to one point at the coil mount under the tank & all black [except ignition magneto black] lead back to that then i'd think everything should work without destroying paint. If you ran a tap through the threads then that should cause anything bolted electricaly to earth. If in doubt just run a wire from an engine screw to the frame or up to the loom earth. I dunno, never had a problem like that to need to find out sorry. But yep earthing is important.

Morley is right, no need to remove any of the powder coating, just tap the threads and it’ll be fine.

Thanks guys , I was looking for an easy way out on this one , I appreciate your help
Thank you for your time

I never really learned electrical, I hope I don't make you feel like a powder post Beatle is boring at your brain.

 My understanding is anything that needs earthing & plugged to the loom black will find its way back to the loom earthing point at the coil.
Black & white probably finds its way back there in a convoluted way to kill the spark when switch is off. [happy to be corrected--well not happy haha].
You'll have a problem if the horn button needs to earth through the bars, but if its a horn button in a switch with other things it may have an earth wire leading back to the loom black of course. Pitty to ruin powder coating. as you'd need to clean it off at the horn button point & the handle bar clamps. Na, must be a better way.
Just found a blury pic off ebay & can see a copper strip which will be horn button earth damn it, so my idea dashed. I'd find a way, run a wire somehow.
That might've stuffed me up for the kill switch on the throttle too unless its got two wires. Sorry i opened my mouth now.

Thank you RT for sharing your thoughts

 

Here's a couple pics of where I'm at with the restoration it's not a perfect restoration but way better than what I started with