Fork swap issues

Ok so I have my 1980 cm400t running about as good as I can possibly ask for considering I run pods because I don’t like the look or have the airbox in addition to can’t afford mikunis. I had a 2011 shadow that was flooded and all the electrical failed. I also needed a front tire on the 400. A friends suggested I swap them and after arguing for a few days I decided why not. I liked it so much I chopped the rear fender off welded it to the 400 and made a real head turner. I love that people like it so much but man I get tired of repeating myself. The problem is that the new forks don’t quite fit perfectly and that results in some pretty bad shaking when making abrupt stops. I have been searching for a couple months and have not found anything that helps me determine what bearings to use that will resolve this. I’d appreciate any guidance on how I can complete this and be a bit safer. I ride it as is and have not had any problems besides feeling a bit uncomfortable in when it happens sometimes. The brakes and suspension are a million times better than this bike ever had plus the size of the tire gives it a real unique stance. Thanks in advance