The Suzuki fork will possibly have to be cut down about 1/4 to fit the Enfield triple clamp properly. The stanchion tube diameter between the top and bottom clamps on the Suzuki forks is reduced, and the distance between the clamps is a bit longer on the Suzuki fork, so the bottom Enfield clamp isn't able to engage its entire width on the full diameter of the Suzuki fork. (hope that explanation makes sense!)
Obviously, the main thing is getting the 26 tpi thread cut in the top of each leg.
I bought the Suzuki forks back in the early 80's on recommendation of an article in the REOC America newsletter. The article claimed the GT750 forks would go right on an Interceptor frame without modification. This turned out to be incorrect, and I had these forks sitting around ever since. (wish I'd had the sense to specify the four leading shoe drum brake, but I didn't know they existed at the time)
The tube diameter is only about 0.1mm larger than the Enfield forks, and I decided to see if there was some way I could adapt these to my Interceptor while still using the Casquette headlamp/fork crown that I want to use on it.
This is actually a lot easier than adapting the steering head races and triple clamp from the Suzuki to fit the Enfield frame. I still wonder what the guy who wrote that article was smoking when he installed the Suzuki forks on his bike.
Oh, and regarding trail and handling, yes it will increase the trail, but the handling should be fine. When I first bought my Interceptor back in 1972, it had a set of Triumph forks on it. I rode it with those for about 5 years before I was able to locate a pair of Enfield forks for it. I always thought it handled pretty good with the Triumph forks.