I always just use the original sleeve that goes behind the balancer, to align the front cover. I just lube the area where the seal rides, install the sleeve into the cover, make sure that the bottom of the cover is pretty much flush with the block, & snug down the bolts. Also, are you certain that the seal itself it installed correctly? The seals flat side goes inside the cover, facing the rad. This means that the open end faces the timing gear. Also, when installing the seal, don`t try to hammer it in in 1 heavy hammer blow. Not only could you distort the seals metal flange, you could also knock the seals garter spring out, either which ccould cause an
oil leak. Are you certain the cover is where the leak is? Other possible leaks near the front could originate from the fuel pump,
oil filter adapter, or dipstick tube. If you are not using the usual dipstick hole behind the
oil filter adapter, make sure that the hole is plugged. Ford used a small soft plug to seal this hole on non front sump applications. I`ve been building and racing FE`s for almost 30 years, the front cover/seal area is one of the few places I have NOT experianced oil leaks from!