Sounds like a headache waiting to happen. How much is your time worth? How many unexpected problems will you find that you have to spend more time and money on? I'd leave it as is and wait for the right buyer. Perhaps you need to advertise it more widely?

For me, I'd rather have an original slant six car than a hacked up car with a V8, unless the conversion is done so well that it looks like it originally came with a V8, which would drive up the time and cost accordingly. I know nothing about your car, but I'd drive a nice clean slant Barracuda all day long anyhow... V8 not necessary.

The market might be better for a V8, but I would suspect that you might be shooting at a moving target. You will obviously want to ask more once you've put more time/money into it, so those folks who don't want to pony up for the lower slant price are probably just looking for a 'deal', and won't want to pay you more for the V8 price. Sounds like you would be taking it off the market for a month or two to get it done anyhow, so why not just wait until the spring, when the market takes off again, to sell it as is?

Just my ...