Lethal Enforcers 1 comes up for sale quite often on KLOV and for quite an affordable price.
So if you were to MAME that cabinet, it is possible but you're looking at a whole lot of effort. Firstly, stay away from the Aimtrak guns. IMO, they don't compare to the CRT guns of old. You can begin your patient search for the Actlabs guns, but be prepared for a long wait and a high premium. Two of those guns will likely cost you as much as you paid for that cab. The other solution is to use Guncon2 guns with Win2Gun drivers. Keep in mind that you are about 10 years late to the party for CRT gun gamine via MAME. That means you will need to use software and an OS from that era. You are looking at Windows XP 32-bit. Check this older
thread I started here on the same subject. Should be able to get you started should you decide to go down the MAME path for light gun gaming.
I had much of the same intentions that you have since I have now. Build a one stop shop MAME cab complete with light guns. But somehow I stumbled upon a ton of CRT cabs for a good price and have been picking up PCB's since. I did manage to pick up a pair of Act Labs guns. But the feel like a novelty compared to my Happ arcade guns.