If it is off by .050"
The only way for your cover to work is to modify the dowel holes so the seal "self centers" then tighten the bolts. However you may run into issues with bolt hole alignment and have to modify those also

If you just replace the seal using the same cover "unmodified" the problem will never go away regardless if it has a slinger or not

I'd buy a quality timing cover or a used O.E.M. install a new seal and be done with it