Thanks for the kind words folks.
Yes, the Tomahawk was a 500 twin. I have the original engine, but it needs new main bearings.
In it's original form, the 1959 Tomahawk had no corresponding Royal Enfield model. As near as I can tell the cycle parts (wheels, mudguards, stays, casquette fork crown etc.) were identical to the 1959 Constellation. The only difference I can see from looking at the parts that originally came with my bike and pictures of 1959 Connies, was that it had a late type 500 twin engine, and a different seat.
It currently has the Meteor style front fender with an Indian chrome tip on it (NOS Apache part from Domi-Racer), and a Meteor rear fender with a later Interceptor stay on it to match the longer Interceptor swingarm that's on it, as well as the early type Interceptor seat, and of course the engine. I guess there isn't much of the original bike except the frame and title presently.
I'm planning to eventually get the 500 twin engine put back together and in the bike. I've always been intrigued by this engine with it's oversquare bore/stroke of 71mm x 64.5 (which is the same as the old Triumph T100 Daytona)
I notice that this site lists various alloy fenders and stays for sale. I'm pretty sure that they've got something that would pass for the original Constellation types. I still have the original rear fender stay, but the bike was missing the front fender, and the rear had been hacksawed.
I was so anxious to get it on the road when I first got it, that I just stuck whatever I had available onto it. It ended up so nice looking that I haven't had a lot of incentive to correct it.
Ready availability of new parts that match the originals make the project more appealing.