On a 248 straight 8, is there a trick to remove the lifters? Do they pull up and are removed? I have never had buick 8 apart before.

Lifter just get pulled up and removed, no trick to them.

I find a 5 lb magnet on a extendable thingy works well.

Sometimes , if it has been years since the engine was apart a sludge will build up on the lower sides of the lifters that makes it difficult to simply lift them out. You may have to spray lots of lacquer thinner or similar stuff on lower part of lifter and continue working the lifter out and back in to get the sludge off enought to get the lifter out. 16 lifter that need this done can be time consuming. I have put lacquer thinner in an oil spray gun

If the above doesn't get it done, I've had some where there is enough wear with the lifter and cam lobe interface that the lifter wear surface is actually upset/pushed and the only way to get those out is to file or dremel that material off-hopefully you aren't going to find that situation-good luck

I did get them out. I had used sea-foam daily for a week with no luck. I removed the crankshaft and all the pistons and them removed the camshaft. This allowed me to see the lifters from the underside. Each one had large amount of crud. They were easy to remove now by pushing them down into the block . From the amount of crud, it would have taken a month of sundays to remove them from the top.