Ha! You will always run into something unexpected, but you can get most of the big stuff done in a long weekend. All bets are off with a serpentine swap, unless you have a local parts store with a Summit Racing type inventory.
Some things to think about:
- Spark plug thread size and reach
- coolant temp sensor thread size
- rocker arms -- standard rockers with guide plates, or self-centering rockers?
- push-rod length
- Will raised valve cover rails on aftermarket heads cause valve covers to interfere with anything, such as AC compressor or alternator?
- Will the new heads' exhaust ports work with your manifolds or headers? Lots of newer heads have raised exhaust ports. You don't want your headers/manifolds or gaskets to cover up even a tiny part of the top of the exhaust ports.
I have had
all of the above problems and more when changing heads from stock to aftermarket. And GM Vortecs cause even more problems.
Hope I didn't rain on your parade.