Trans pan ID's trans as TH350, It has a 10 bolt rear end. My guess is both of those as well as the drive shaft will need to be replaced to live behind the 454.
The paint looks good except near the door panels. Bad masking job on the panel or they didn't remove the panels to paint the car. Makes me think it's a wham bam paint job sloped on to sell the car. They don't call it resale red for nothing. A nice paint job can hide a lot of problems that will reappear in a few years.
He says it has new quarters on it. Wonder how good of a job they did installing them. Check the trunk drop offs and inner fenderwells too. At first glance I didn't notice the new quarters. Gaps look pretty good and so do the body lines.
Trunk stripes look too wide. Bothers me, might not bother you.
Interior sail panels look badly done. Another sign of a sloped together rush it to sale job.
Engine compartment, same signs. Rush to sell.
Bottom of the car looks pretty good. It's the only part of the car that looks better than I would expect.
I wouldn't go any higher than $14,000. That would be based on a basic Chevlle, with a decent paint job that someone dumped a 454 into. Before you make that offer, better inspect it in person for signs of a rust cover up job.