The Reflector condition makes a HUGE
difference , no point putting brighter flasher bulbs in if the reflectors are poorly or shot . it might make them look brighter to look at but still be throwing little light forward.
worst I saw recently was one of those horrid W8 Passats that failed its WOF because the headlights were that bad they were not even registering on the light meter & it had HID headlights
Turns out the HID bulbs were working perfectly, but the reflectors were completely shot & so it now had just 'super bright' light bulbs in effectively a black hole.
Back to the 58 , Make sure all your wiring connectors are cleaned up. easy with these as you have the screw connectors & your headlight fuses have their own little fuse box in the spare wheel well. Also the contacts the fuse its self makes can be cleaned up to all make a difference
Same with the screw connectors at the bulb holders.
Failing that, I have some brand new Genuine pre 1960 headlight reflectors I've had for 30 or so years , you could always make me an offer I cant refuse
( might be cheaper to get your old ones re-chromed )
A 'Cost effective' option is what I did to my 1960 Beetle back in the 1980's , I fitted some brand new Bosch Driving lights that still looked period enough & changed the bulbs to 6V Halogens .
Worked a treat, Super simple to wire in too with the screw type connectors you have I wired them direct to the high beam (no relays, no extra switches etc) & every time I selected High Beam, they came on too, it was Brilliant.
Made a massive difference on the open road & I mounted them with a small bracket I made up that bolted directly to the bumper brackets using the existing nuts & chrome bumper bolt & ran the wires directly into the wheel well ( where the fuse box is ) through the same outlets in the body that the bumper irons come out so all in all, super simple fit & can be removed with out one sign they were ever there.
Photo below was taken about 1986-87 ( I miss my Mk1 Golf it was only 5-6 years old when I got it, it had the factory 4 light grill so was great light wise too