A good source for ready-made brackets strong enough for this task is HD/Lowes in the electric aisle. Look for the Unistrut, or "Sturdi-strut" or whatever product line, alongside the metal electrical conduit. They have pre-made L-brackets of 1/4" steel, with either one or two holes per leg. This stuff is strong, but still workable by hand-held tools if necessary for filing, drilling, or cutting. It's about twice the thickness of the original brackets. It would be quick work to cut off the excess, drill a new (smaller) hole, and fasten it with an additional fine-pitch nut and washer on the original long head studs.
Jumpin' Jan S. has made a custom pulling bracket that also fits nicely. I believe it's outlined in the Marque PDFs.
If you're pulling engine and trans together, just be sure that whatever you use is stout enough to lift both (easy) at the extreme angle necessary to clear the bodywork (not so easy). In other words, the factory lift points are more than adequate for a straight-up lift of the engine only, but I'm not sure I'd trust them for engine+trans at a 45-degree angle. (That said, I believe others have done it successfully. It just looks too risky for my taste...)
In addition to the "right" places on the engine to lift, I have used S-hooks (old-school 5/16" heavy ones) in the hole at the corner of the engine mount (left side) and a similar one on the right side, near the fuel pump... then a bracket at the rear. The three points proved very stable for lifting.