The QA1 is perfectly capable of supporting the big block. More so than the stock K frame. What was done to beef up the original K-frame design to support a big block? Nothing. A big block K and a slant 6 K are identical except for the engine mount locations. Nothing was done to strengthen the K for the big block compared to the slant 6 or small blocks.
As for jacking the car up, that’s exactly why your original K-frame is caved in. Seems like that’s not a good argument for staying stock. Sure, you can weld a skid plate onto the stock K to reinforce it (which is what I do with all of mine). But you could do that to the QA1 too.
