In my experience no cheap aftermarket relay setup comes close to what Ford had to offer from the factory. In your place I'd stop wasting efforts on trying to figure out *** relays LMC used, and instead head for your local U-Pull-It salvage yard and look for a "whale"-body ('98-up) Crown Victoria - on the passenger-side inner fender behind the battery you should be able to find this critter:
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Not all "whale" Crown Vics will have it, as IIRC it's part of the ABS system and a Crown Vic could be ordered w/o ABS, but it really shouldn't be hard to find a retired taxicab or police interceptor that has the box. And you want it because it contains two Bosch-style relays, one is your typical 40-amp relay with 14-awg power wires, but the other is a 70-amp beast with 12-awg wires and monster terminals for them. This is what said box looks like with cover removed (grey relay is the 70-amp one, and black is the regular 40-amp, both are the same size so that should give you an idea for dimensions of box itself):
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The box is held to the car's inner fender with a metal bracket with two studs pressed in it, nuts for those are on the wheel side of the fender and take 11mm (7/16") socket - save the nuts and chop as much of the wiring coming out of the box as possible, this will make mounting the box in your truck very easy and tying it into your wiring as simple as butt-connecting it all. Heck one of the 40-amp relay wires, yellow w/ light blue tracer, has a nice weather-proof connector on it as it bridges the gap between the fender and the engine, so chop it right where it disappears into the engine harness and you get said connector to go with the box. The box cover actually has a foam seal on it, and if you dab some dielectric grease in the holes for the wiring terminals on the underside you end up with something that is essentially sealed against the elements (and apparently power steering fluid from a blown return hose, also pictured above, lol). The box pictured above is as mounted in my bricknose next to the cruise servo, sorry I don't have pictures of it in its stock location in the donor Crown Vic taxi cab but like I said it's behind the battery and near-impossible to miss. I've actually use those boxes for home-made headlight relay harnesses quite a few times, typically assigning the 40-amp relay to the low beams and the 70-amp one feeds the more powerful high beams.
If you have extra lights you just add another box and wire it accordingly, or, if you're very lucky, instead of the 2-relay box pictured above, your Crown Vic donor can provide you with this instead:
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And inside we have these guys - three 40-amp relays, and again one 70-amp one for the Crown Vic ABS pump motor (or whatever):
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Those boxes are kinda rare tho, I've only seen a few, and salvaged just the one pictured above - this one is again in my bricknose and it has the same benefits as the more common 2-relay box, just contains 2 more relays and thus saves you the hassle of mounting two of the regular boxes side by side if you don't need more than one 70-amp circuit.
Also, I've seen the 2-relay boxes on some OBS trucks equipped with factory tow package, but I think those contain two 40-amp relays, which is still plenty enough even for a pair of 120W Daylighters (and your factory lights are actually about half that in power even on high beams) - that box lives right next to the power distribution center on the driver side inner fender, if you find one of those just use that instead of the Crown Vic box, it'll work just as good.
