cal78, Marty was correct when he said its the "age old question". Condition condition condition says it all. First I'd think you will take off the fuel tank. I just can't see you driving around in a truck with a fuel tank on the back of it but them??? Maybe so.
I usually turn to the Old Cars Price GUIDE which has been following auctions and sales for over 40 years. Its just what it says it is....a GUIDE. A personal look at the amount of body work, tires, bumpers, upholstery can quickly tell you if you buy it, spend some money on it, will you then have more money in it than it'll ever be worth!!
Being a fuel truck is it a 1 1/2ton?? The size will help determine value. Using a one ton stake truck for comparison the guide list it as #1 condition 23,000 #2-16,100 #3-10,350
#4-4600 #5-2760 #6-920 so from a #6 parts vehicle to a #1 show truck there is a LOT Of room to move around. Does it even run. If it does, is it smoking,rattling,ect?? Just from the few words of your description I'd probably offer the guy a 1000 but even then this truck should be in pretty decent shape as it will become a "money pit"....... For some reason I just can't see 5 big ones on this truck....let us know how you come out. Its good info and helps others when shopping.
The comments are just my .02 so good luck.
