I never noticed a difference. I have a stock 70 300HP Monte and a stock 72 350 Monte and there does not appear to be a difference. I have bolted other small block valve covers (just ones kicking around, not sure what they were from) to my 70 before without problems also.
I'll be going via I5 since I'll be in the Vancouver BC area a couple days before the meet. I plan on driving down on Thursday. Hope to meet up with some of you along the way.
Whether your Monte is ready or not, you are going. No negotiations. I'll pick you up on my way to Oregon if I have to. I've seen you miss too many meets already.