I'd say $3K-$3500 would be a very fair price for that car, but it'll probably go for less. I know you said it has the Astroroof which is rare as hell, especially if it doesn't leak and it works well. Does it have buckets and a console too? That'll improve the value too. Also, I doubt it has the HO 305, it probably has the regular LG4 305. If the 8th digit in the VIN is a "G", then it's an HO motor, but even the Pontiac 2+2 (AKA Aerocoupe wanna-be
) came with the LG4.