Where do you find manifold casting numbers listed? I have a 261 engine that needs the pair of manifolds. I have been sent in error a very nice looking pair with intake casting number 3835627 and exhaust casting number 3835988. If these will fit my 261 I'd rather not send them back. I would need to enlarge the vacuum fitting on the intake to accommodate the large service needed for a Hydrovac brake booster and a 2-speed rear end.
Is it very risky to drill out and tap the manifold for a 1/2" pipe thread? With shipping, the cost was $175 -- pretty high, but no truck without them.
Thanks for any advice.
