Help price guide

Dropping in. Have had 2 ford lightnings over the last 7-8 years. Looking at a few single cab 5.3. Found a white one with a few mods 91,000 miles. LTs ,CAI, tune dropped on LTZ wheels. White. Clean looking truck. He is wanting north of 11-and some change. Not sure what they go for or what would be a far price to offer. Personally I just want something simple, ill do heads and cams im sure. Just looking for s good starting point. Thanks again in advance.

What year?

the Truck im looking at is a 2005 with 91k on it with Kooks LTs full exhaust intake ,tune lowered on LTZ reps.

So take the blue book value stock, add up the cost of the parts and figure out if the truck is worth that price to you.