Wellcome to the “Tired 318 Club”.
I have / had the same problem with my 318, but fortunately there are a couple of ways for you to go. One for example is overhauling your 318. Gary Pavlovich is the man to ask. With very few modifications and a better cam you can get a very good performance out of it. If you consider to go for a 361 then you’ll need the motor mounts and also the correct bell housing (if you use the A-466 TF).
There is a thread in show your ride, if you’re inerested.
Good luck!
Stefan