That's the nice thing about the aftermarket. If you want to do anything major to the engine, rebuild the original one, with those hot boy parts, but not with the intention of building a powerful engine, just a reliable one. I did this with one of my Jeeps. The "AMC" 4.0L I6 is a fantastic and reliable engine already, especially towards the final years, but one of the big problems with them came down to bad machining on Cylinder #6 (closest piston to the firewall), which gave it a sort of oblate shape that would wear down the pistons and wrist pins, which were crippled by bad metallurgy.
Knowing that there were factory faults with those parts, I went for the performance options. Forged pistons, aftermarket aluminum performance head, AMC 4.2L crankshaft for increased stroke, stronger connecting rods, and we bored out the intake manifold to take a bigger throttle body. The exhaust manifold was changed out for a performance header, as well, because they are liable to crack, being cast iron. The power it made gave you just a little bit more seat-of-the-pants feel, and I know that the engine is going to last another 400k miles, if nothing got overlooked, because it was completely refreshed with parts that are far stronger than what it came with. If something fails, it's going to be in the top end., which probably won't be bad enough to ruin my week, because I still have the original head, which I had decked with the performance one and the block. Fully rebuilt, waiting for a catastrophe in my garage.
If you want to put money in an engine, do it that way. Find weaknesses and eliminate them. That makes the difference between power, and reliable power.
