Just. Buy. One. Of. These.
I've bought a fair few tools and bits and pieces for this project. So far, I have pretty much only been working on the donor car, so have used hammers, breaker bars, my socket set, spanners, pliers.... and so on. All useful and expected. The one thing I didn't buy up front but very quickly decided to invest in was this. Seriously - if you are breaking a donor car, just buy one. It will save you HOURS, possibly even days of sweat and tears, skinned knuckles, swearing, aching muscles, and ruined tools (oh, and get an inexpensive set of impact sockets as well - regular sockets can explode with the amount of force it generates. If you are breaking an MX5 - get a set that goes up to 32mm. You'll realise why when you come to the rear hub nuts). It's a 1/2 inch impact wrench and it's a beast for removing rusted up, over torqued, stuck nuts and bolts. Garages have even more extreme pneumatic versions but the 18V battery versions are perfect for the home hobbyist. All my 18...