i have state farm. my agent is
www.dickmichael.com i was quoted $46 per 6 months with a value of $15k originally but then found out that upping the value to $25k only cost about $10 more every 6 months. due to the age of the car the only source they use for value verification is nada which lists an 83 targa as having a high retail value of $22.8k. I opted for the $25k value since there was no real way for them to dispute it and my agent agreed.
there are no restrictions at all. the car qualifies as a collector thus the reduced rate. in ohio we have 3 types of plates - regular, collector and classic/antique. classic only allows you to drive in parades and to shows but not daily or even weekend driving. once you buy the plate you are done for life (no renewal fees). the only restriction for collector is a car over 25 years old but it costs $10 per year more than regular (and it looks different).
normal
collector
classic/antique plates are issued according to the year of the car. so if you had a '78 the plates would look as they did in 1978.