I assume you mean replace a V-8 with a V-10. You can't just add two cylinders. Yes, it has been done, but you and I are not going to do it. There are so many differences and modifications that you are 100 percent guaranteed of butchering a nice car and it WILL end up with a "For Sale As Is" sign in the window. The radiator, transmission, drive shaft, torsion bars, engine mounts, cross member, transmission mount, and entire exhaust system will be different. You'll need all the computers and controllers which work together with the instrument cluster, and all the wiring harnesses. You'll need the high-pressure fuel pump which won't fit in the gas tank. Your gas tank is vented. All newer engine computers monitor the fuel system for leaks and for emissions so you'll have to figure out how to seal the gas tank and fuel supply system. You'll need two catalytic converters and oxygen sensors which are not part of your current exhaust system. The power steering pump will not bolt to the new engine. Alternator and air conditioning compressor will mount differently. The newer AC compressor will use R-134 refrigerant which is not compatible with the R-12 used before 1994. All the hoses and plumbing will be different.
The person who did this custom job had a smashed Viper to rob all these parts from. It took him a couple of years and a REAL lot of money. The entire firewall had to be cut out and be custom fabricated.
If you have a small block V-8 now, particularly the 318 c.I. Your best bet is to look for a 340 c.I. I have one in a '72 Challenger and even though it is tired it has more than enough power to pass people when necessary. The left engine mount needs only a minor and easy modification. A 360 is a lot easier to find and the valve seats can be ground bigger to install the larger valves used on the 340s. The runners are the same so you'll have just like a 340 but with larger and beefier crank shaft journals. All small blocks bolt to the same transmission bell housings.
If you have a big block V-8, the 440 is your best choice but you'll spend a lot of time at the gas stations. If money is no object, buy a 426 hemi crate engine. The cross member and engine mounts are different but it will bolt to the same transmission as all other big block V-8s.
Keep in mind that when it comes time to sell that car, it will bring the biggest price if it has the original engine, regardless of the size. If you do dump something different in it, keep the original engine to sell with the car.