You'll find every different size of motor in these cars. The majority being 1915 or below due to a variety of reason. Then there's the rest of us for which nothing other than HP will suffice. Starting at 150 hp 2210's on up to I think a 2376 that someone on here is running. There may be larger but I can't think of what size it would be. And lastly there is the crowd that went water cooled Subaru and will probably never look back. As ZFNHSN stated, decide how you want to drive it and build it from there. You can drive a fast car slow and you can drive a slow car fast but I think you'll reach your limits much faster and might grow bored if spirited driving is what you seek. Top down, star gazing, bird watching, wine tasting, sunny days and cool nights with the rest of the world passing you by is okay then there's no need to go big.