Electrical (I hate electrical problems)

:gonnablow yeah, they can be sooooo frustrating.
So, I have a 91 xj 4.0L, and lately, my radio and clock have been blinking out and then back on. usually just once, but sometimes (usually on a steep decline) they will blink repeatedly. I don't know, maybe a bad ground or loose wire? it's got the stock radio, and I haven't messed with that. I messed with the ignition system and wired in a push button start with the accessories going to a toggle switch, but I can't duplicate the problem by messing with the wires, nor can I get it to happen while messing with the battery terminals.
Also, on a potentially unrelated note, the guages have a tendency to freak out. my headlights will get dimmer, the volt gague reads about 12v, the temp gague reads hotter than it actually is and the gas gague reads lower than it really is. seriously, it's got me all messed up.:banghead:

any help would be greatly appreciated.

Mains grounds:
1) Battery to Chassis
2) Battery to Engine Block
3) Cylinder Head to Firewall.

Clean/replace as required. Clean the ring lugs, and clean contact patches on the chassis (you only need to go about the size of a regular postage stamp, max) down to bare metal. Apply corrosion inhibitor (find it in your hardware store's electrical section) on reassembly.

Auxiliary grounds:
1) Engine block near dipstick bracket
2) Should be one on the driver's side fender liner
3) May be one or two under the dashboard. Check the driver's side kick panel (may need to remove liner panel,) and check near steering column screws. These would be the main grounds for your instruments and switches. Service as above.

Since you don't report trouble with the rear lighting, you probably don't need to look at it - but it should be tied to a chassis pillar behind the driver's side cargo area liner. Clean as above.

A Scotch-Brite pad or wheel or a wire wheel (I use brass wire wheels) works well for cleaning ring lugs and for stripping metal. If a ring lug is dirty or corroded beyond cleaning, replace it (typical hardware store stuff is tinned copper, and perfectly acceptable.) Replace dirty/corroded screws out of hand, with a preference for brass (machine threads) or CRES (tapping screws.)

I find it useful to use brass flat washers under the screw heads, since it will increase the contact area between the ring lug and the fastening point (you've cleaned the chassis contact patch under the ring lug, and you'll sandwich it between the washer/screw head on top and the chassis down below. Again, probably overkill and doesn't do much, but it makes me feel better if nothing else.)