Nash: I think that everything will be fine. It had been so long ago when I looked at mine without headers (1977) I forgot what it looked like naked.
In 77, I put on a set of 3 runner Doug Thorley headers, and I paid about a buck, maybe a buck and a quarter, for them. For whatever it's worth, they looked just like the ones you bought, and, amazingly, they fit! and they went on without much problem.
You probally remember my gripe with the replacment set of 4 runner, Hooker Competition Plus that I bought in 1987--and I paid something like $380 for them. They fit like socks on a rooster because the cheapskaets made them for 67-81. In addition to them simply not fitting, I had an oil filter adapter interface problem. I don't recall what I ended up doing: I had an old and a new style adapeter, and there is a difference in the angles. I think that I had the old style on and have to change it to the new style, or vice versa. I was pretty ugly by the time I got the garbage--that wasn't made for my car--installed.
To back up to the Doug Thorley headers, I think that I simply weaseled them in, and I may have even dropped the right side in from the top, and I think that I installed the left from beneath the car.