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The 400 HP engine had 2 bolt mains. Externally, the 4 bolt block has larger oil passages drilled over the filter - it's obvious if you look even as installed in the car. You need to slow down! I have seen many blocks on e-bay = I have watched and bought them for the past 5 years. You should be able to get a late 439 or a 270 or early 512 2 bolt block as std bore or good 0.030 for $1500 or less. For the 2 bolt blocks, it seems most are cast up to 2 mos before the assembly date, frequently closer. I have seen a number of 4 bolt blocks that were quite far off.
The cranks are a dime a dozen, and the heads are still really cheap too - less than $200 for a good pair if you shop around. The intake will cost as much or more than the block so be prepared!
With this e-bay engine, you would loose points for the suffix code (LR) and for the VIN derivative. You could get the exact same number of points with an Impala LE code block - as long as the dates are good, you would loose for the suffix code(LE) and the VIN derivative but still get all the points for the casting number, casting date, and machining dates!
From a dollars for points perspective the Impala block is a bargain - two recently sold on e-bay for about $1000 each! As far as NCRS is concerned, unless your car was a 435, that LR code is just as incorrect as the LE code. Let someone with a 435 get it for their car, save your cash for the intake setup.
Big blocks were only cast at Tonawanda during this time period. The castings for 1969 were 439, 270, and 512. In each given casting, all the block castings were identical. The machining was different for 2 vs. 4 bolt mains, but a 2 bolt block can be converted to a 4 bolt by adding the caps, drilling the oil holes above the filter, and adding notches to the tops of the bores for valve clearance.
So, there is no such thing as a Corvette block casting - the Impala block is identical as long as you compare 2 bolt to 2 bolt main. Almost all big blocks from the 60's and early 70's say HI-PERF even the 396's.
The only difference for the Impala block is the suffix code and the VIN number. As for restamping a block, it can be done but the hardest part is to duplicate the broach marks (the finish of the pad). If the judges can tell the finish is wrong, you loose the points for the pad finish and machining dates as well - is it worth it? At least the Impala block still has original broach marks.
Can it be done successfully? Yes, but it'll cost you and there's no guarantee it'll pass judging. For now, I would just get the Impala block. Later on, once they've perfected the broach marks you can always choose to try it on your block. Before you do, I would recommend you go to some shows and look at the original low HP engines (less likely to be restamps) and see what an original pad looks like. The more you see, the sooner you will see how hard it is to perfectly reproduce the original style broach marks. Some engine builders will try to just sand the pad with a belt sander, but then you can tell it's lower down than where the head bolts to the block. If you want to do it correctly, you need to "re-broach" the entire deck surface. In addition, the original broaching appears to be a lot of short parallel lines made as the cutters chatter over the deck. A lot of the restampers use a giant belt sander but that leaves each individual line running the entire length of the deck - no chatter marks. As for the stamp characters, they were unique in style too so a whole book can be written on that as well.
I think you only get about 50 extra points for the suffix code and the VIN, so you could make up a lot of that by getting the "bonus" points for a fire extinguisher, battery cut off, and NCRS sticker. You could do even better if you drive the car to the show and get points for mileage too.
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