Well I rebuilt a slant 6 years ago and also a chevy 350 and always used a high volume pump in the rebuilds even though they were stock, never had a problem with them, just gave a few extra pounds of oil pressure as they wear out so you get more life out of the engine. I drove the slant 6 for 15 years and the chev has been going for over 10 and still going strong.
I compared it with the old pump and all you get is a slightly wider gear in it. Its a loose engine too so I don't think it will be a problem. The extra volume should do it fine. I prefer that than having low oil pressure. I expect the 250 to last 10 or 20 years or longer also.
