Engine selection help

Hello a couple buddies and I are trying to build a buggy or a sort of extreme go kart and was just wondering in regards to the engine, as I was looking at getting a old car engine and was wondering if you could help me out as from what I understand the engine comes alone and I'm not sure about what other things I may need to get the engine running because we watched some videos about wiring and stuff and we're just completely lost about all the wiring and connections and I read somewhere about an ECU.

So any help would be greatly appreciated as for example a leaf blower engine all you need out the box is a tank of fuel and I was wondering in short all the necessary things we would need just to get the engine running.

I'm sure this seems silly however as I said all help would be appreciated, thanks.