John; that's not the same Holley I have on my car. Mine is the Holley 0-9895 that is sold by Holley Performance for $899.99 on E-Bay. Paul
OK, yours 0-9895 is no longer available, per the Holley website. That may explain the cost.
One thing that I haven't seen anyone say, besides me, is if you go from a spread bore to a square bore carb, you have to change the intake manifold. That's something to remember that there is more cost because of that. They do make a spread bore to square bore adaptor, but it's probably going to cause more headache than it's worth.
In other words, figure that into any costs. Just a quick look on eBay shows a minimum of $150 to $175 for a used manifold including shipping. $25 for a gasket. There are some offshore sourced aluminum intakes for $250 or so, but I'm not sure on the quality (again, possible headaches).
IMHO, I'd rather rebuild (or have it rebuilt) a running, working carb over buying new and screwing around getting the jetting and other settings right. All your throttle and trans linkage will fasten right back where it was without adding any more hardware. New doesn't equal good, nor does it mean no headaches. Cost to rebuild is less with less headaches.... and if you use Woodruff carbs, he will test run the carb before sending it back to you.
I used the word "headache" a lot in this post... For a reason. But, I'm a glutton for punishment and recently switched my Thermoquad with its spread bore manifold for an Edelbrock AVS and a square bore manifold. Covid knocked me down right after I got it done, so I didn't get any amount road time in before it was time for me to put it away for the season. I still have to get it tuned right.
