Matching numbers has been discussed a lot on this forum and the general opinion is that it is nice to have and can be a decider in a purchase if everything else is equal but given that there was only ever one engine size for each model, the need for matching numbers does not gain as much importance as it may on say a Mustang.
Having said that, with receipts for the engine work and knowing that it is a new block and head is a real plus in a purchase and to me would be a big decider in a purchase. I purchased a 230SL recently knowing that the engine needed overhaul and the price reflected that. Now that the work is being done, I probably under estimated the cost by as much as 30-40%. No change out of $10k by the time it is all done, including re-plating of all parts, new head, pistons valves etc etc etc. so a new engine capable of second or third rework is very good and also has value.