I'm almost afraid to get involved in an
oil thread. But, here goes:
Don't assume you have a flat tappet cam just because your mechanic used Delo
oil. Lots of people used diesel oils because they had more
zinc and ZDDP for a while. As said above, they no longer do.
Contact the last shop that rebuilt your engine and ask them specifically what cam is in there.
You should also ask them specifically what
oil pump is in there. There's no reason to install a high pressure pump in a Windsor motor. Sometimes, though, a high volume pump is needed. Particularly if you have external oil system components.
Hot idle pressure for a Windsor engine is generally about 25psi or so. The factory specs are rather vague. The pressure relief valve is usually set to open at about 60psi. Comparing factory specs of a FE motor to a Windsor motor is kind of pointless.
Using a straight weight motor oil these days is really not a good idea. There are huge advantages to the multi-weights, and you should (IMO) take advantage of them.