Does this seem like a good deal?
Offer him 7k, don't pay more than 8.2.
Would this be a horrible daily driver?
It's a loud, coarse, heavy vehicle that gets 8-10mpg and probably won't go over 70 mph as it's geared. The clutch and transmission are very hard to operate to people not used the force necessary to use them (your left leg will be twice as thick as the right and your right arm will be like a railroad tie). Despite this, it was my favorite vehicle to own. The seats are squishy, the leafs can be firm to harsh depending on the kind of lift it has.
Is it correct to think a professionally done V8 conversion is upwards of $30k like I read online?
This truck has the 2F engine with new headers and carb, not a V8. Conversion to a V8 will also need a transmission to be done properly. Most people go for the 4.8L GM with a four speed hydramatic AT. I think 10-15k would be more fair for the engine conversion, if done right. Don't waste money on a V8 conversion unless you plan on restoring the rest of the truck.
I would buy this truck if I had the funds and time, but I already have an 80 series I'm working on.