Jim..I reckon you'd be letting the engine down by building it as a pre '70 machine. It'd be way off the pace compared to the 2 strokes or even the B44 Beezas. Build it as a pre '65 by putting it in a BSA Goldy,A50,A65 style frame. They were the hot ticket back in the era or you could find a genuine Ariel frame. Is the engine a Red Hunter 350? The hot ticket is a Metisse MK3 or Cheney but I doubt you want to spend the big dollars for a kit. If you can't find a BSA frame I'd be looking for an original Ariel frame and lighten the crapola out of it. It's amazing what you can achieve with a hacksaw, a grinder and some lateral thinking.
I'd use either CZ or Betor forks, CZ magnesium hubs and a nice alloy or fibreglass tank.
John Selva from Victoria has had some amazing success in pre '60 and '65 VMX on his nice HS Ariel over the years so they can be put to good use. Below is the most famous Ariel of all time, Sammy Millers beautiful GOV132 trials bike. It's not really a scrambler but there wasn't a lot of difference in the day. There's a good feature on this bike in the latest Classic Dirt Bike.
Although this is a Matchless powered BSA, you get the idea of what I'm talking about. Imagine an Ariel engine in there.
