if you do any evening cruizing it is well worth it to convert to relays, the old system has headlight current flowing through the firewall and to the switch causing voltage loss to the lights, not to mention a ton of 40 yr old wire insulation being ripe for a fire hazard. It was one of the best mods Ive done to date, the tail lights are even brighter now.
I got a relay kit from http://www.modernvintageauto.com/index_files/page0006.htm
Very good quality kit, plug and play install. $40 on the web page but I got it for $30 since I'm a member at Vintage Mustang Forum. Shipping was $12. For the price of the kit, I would not consider DIY.
thanks guys, im going to order the new headlight switch, then if i still have problems with the lights, i will turn to the wiring and relay kits...thanks again for all the help