Flywheel and Flexplate are essentially the same thing, if you have auto trans your dealing with the flexplate. This is a big flat disc that mounts to the back of the engine to the end of the crankshaft (which sticks out of the engine and is sealed so soil doesn't spill out by either a 1 or 2-piece seal). The flexplate is sandwiched between the crank shaft and torque converter and is held on by a handful of bolts to the end of the crankshaft and another group of bolts hook it to the torque converter. (The torque converter looks like a big donut and acts kind of like a hydraulic clutch so when you slow down the engine can keep turning without turning the transmission input.)
The flexplate also has teeth running around the perimeter, these teet are what the starter engages to start the engine. So if you want to see your flexplate, take off your starter and peak in the opening behind it and you can see the teeth on the perimieter of the flexplate.
When putting in a new engine, get a new flexplate if your looks warped or has any missing teeth, they are not expensive so maybe just get one anyway. Just be sure to torque the bolts correctly to both the crank shaft and the bolts connecting the flexplate to the torque converter and use some loctite. I've had some bolts work loose that I failed to torque corretly and it scares the CRAP out of you when you think your new engine is making a horrible knocking noise...when in fact one of your flext plate bolts to the torque converter and ticking against the trans bellhousing!:shocked:
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Will it be easy? No. Is it doable and will you have fun and be proud? YES!! It doesn't matter what engine you get it won't be easy, the engine and components are not the hard part, so it doesn't really matter which engine you get. For example. The hard part is all the stuff that is impossible to plan for. In my case, my cherry picker wasn't able to lift the engine high enough to clear the front clip. So I had to remove the front clip. And I live in Wisconsin so the huge 3/4" bolts and nuts that support the body mounts under the radiator support were copmletely rusted would just spin in place. The bolts were down inside metal stampings that made it impossible to get at with a grinder. Getting those two bolts out took 50% of the time to do the engine swap. bolting the engine in and attaching new parts, that is the fun part, it is like playing with legos. It is all the extra stuff required to get to that point that will drive you nuts (siezed fastners, fuel lines that bend and break when trying to unhook them), but the creativity and challenge of overcoming these same hurdles will also make you so proud and happy when it is done. And you WILL get it done, and learn A LOT in the process. And no matter how hard it is when you're done, you'll look bak and go "That wasn't so bad!" and then you'll start convincing other newbies to go for it, and having thoughts like "hey I coudl buy that truck with the blown engine...all I need to do is throw a new engine in!!"