Disclaimer: factory frame and engine mounts replaced with aftermarket solid (possibly shorter) previously and a 1/8" mid plate was installed so at least some grief was self inflicted.
So it only took about a dozen shots to clearance the crossmember for the Doug's D326 headers, relocate the passenger brake hard line, and tweak the passenger side of the mid plate plus relocate it's mounting tab on the frame rail. I was expecting the clunk as I lowered the engine in, but the passenger side having a tube wanting to occupy the same space as the mid plate had me scratching my head for a few minutes. (These headers don't fit with a mid plate) This is after mucking around moving the firewall so a flexplate shield will bolt in for a couple of hours with the required engine Re and Re's.
This is basically a race car now, and it's been years since I worried about bashing, cutting, and heating on this thing, a valuable restoration this shall never be.
That being said, Doug's did a fantastic job of running these massive tubes while occupying 100% of the room GM gave them. The starter access is fantastic, and the oil filter is easy access. (Previous Hooker Super Comps with a kick out sump pan required me to pull the header off the head to remove the oil filter, annoying as you learn about it with hot oil draining as you try every way to extract the used filter and cannot) These things are heavy, with thick flanges and thick tubing, and the finish is beautiful and should last many years on a street application. I can't bring myself to drill holes for my pyrometer and evac-U-pan tubes. They are also tight to the floor pans, higher than the aluminum pan on my turbo 400.
I just wish I had a chance to dyno with them, I'm fairly certain they are worth power over our dyno or my old headers (1 3/4)