Howdy Ponyman:
Good Question and I appreciate your descritpion of your criteria. That helps to form these suggestions. 1st off, What year casting # are you working with? What trans? I'm guessing that this 170 is in a Mustang???
In general when you are doing a top to bottom rebuild it is likely that you will be replacing the cam, cam gears and timing chain, and lifters. You would be wise to not buy stock replacement parts. Best to buy; an aftermarket cam with 260 advertized degrees of duration and lift in the .400" area, a double roller cam timing chain and gears, high quality hydraulic lifters. The right cam will allow you to maintain idle quality and vacuum, and still significantly increase 1,500 to 4,500 rpm performance.
The rest of the bottom end is solid and a basic rebuild will refresh it.
The head is where you will find the most help, but avoid a few pitfals. Be sure to reread the sticky at the top of this forum on "Swapping Heads". Any stock head will benefit from a 3 angle valve job, back cutting the intake valves, polishing the chambers, and measuring chamber volume to confirm your goal Compression ratio.
Finally, your intake, exhaust and ignition systems need to be coordinated to get the most out of the package. The stock system can be improved on, or upgraded. Your choice. The year and type of carb and distributor will be critical considerations if your mix and match.
Your goal of "be comfortable on the highway" will also involve gearing and tire sizing. Start by assessing your rear gear ratio and tire size. Higher gears, lower numbers allow a lower engine speed at 65 mph. If you currently have a 3.5:1 rear gear ratio, changing to a 3.00:1 will lower engine rpm at highway speed, but hurt acceleration. What tranny you have will help in the mix. For example, an auto with a torque converter will help to make up for a too high rear gear.
If you will add more information about what you will be working with we can be more exact in offering suggestions.
That should get you started.
Keep us posted.
Adios, David
