Out in bad weather after dark last night and began wondering if my Sylvania sealed beams could be improved and how to do that: I put on the foglights, which helped. Im old I know, and probably night blind, but other than spending 500 on replacements, do I have any options? They seemed dim compared to our other cars. No obvious signs of voltage drop.

My Hella Lights :: Vision Plus 7" Round Conversion Headlamp

I did this with 80W/100W H4's on my 1983. Cost about $150 total and made a WORLD of difference. Never got flashed with the low beams on in the 5 years I have had them. Turn the high beams on and it lights up a straight stretch like daytime. I just added relays to the lights to handle the extra wattage.

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2012 Mercedes ML350 Bluetec 91K (hers)
2005 Corvette 55K (fun car)
2002 VW Jetta TDI 231K (mine)
1998 Volvo S70 T5 Turbo 196K (kids)
1994 Ford F150 4WD 249K (firewood hauler)
1983 Mercedes 300D 376K (diesel commuter)

No magic involved and wont get something for nothing. Gimmickry is colored lights and LEDs are a non-improvement, so avoid both. H4 is a big step up in performance and modest up in price, then you can look around for bi-xenon stuff which would be a (very) modest increase in performance for a huge increase in price.

In the H4 area you can go with Hella which are fairly cheap ($100) with commensurate performance, or look for Cibie which cost more ($200) but have noticably better performance. I would avoid any funky sealed beam halogen stuff, stick with "E-code" H4s.

I just picked up a set of Cibie from here for about $220;

https://www.danielsternlighting.com/

HID projectors are a huge improvement over anything halogen.

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CENSORED due to not family friendly words

Contact Daniel Stern and get some Koitos.
Google "Daniel Stern lighting"

My Hella Lights :: Vision Plus 7"x6" Conversion Headlamp

Get the ecodes. You'll be happy.

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1991 300D 2.5 "Rocinante"
2002 Golf TDI "Teen Spirit"
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1984 300D
1966 Mustang I6 3sp
1985 Mazda RX-7 GSLSE
1982 Toyota Supra
1977 Datsun 280z
1971 Datsun 240z

Did you check voltage at the headlight connector with it plugged into the light? Given power needs to flow through the headlight switch / dimmer / fuses / headlight plug, there are lots of places to lose voltage.

Consider as a first step adding a set of relays and powering the headlights directly off the battery ( be sure to use fuses as close to the battery as possible. ) If you go with brighter headlights, this is an absolute must as the stock system won't be able to carry the additional current.

What is the charging system voltage at the battery with headlights and other typical accessories on and and engine up to driving speed?

Do you have old style tungsten headlights ( exposed filament inside the headlight ) or halogen ( small bulb surrounding the filament ) ?

Lastly, how old are the current bulbs? Incandescent bulbs wear out before they burn out because tungsten coats the inside of the bulb reducing light output. .

I suspect they are very very old.