Real question is what are you trying to do ?
Do you want to do the modifications necessary to put another engine in because the engine is less expensive? Or, are you looking to up the power significantly?
If you are upping the power, you will want better suspension, and brakes. All of this adds up, so if you are focused on a specific goal and want to look at total costs and time, it is a longer route, but it will yield a unique ride that will be a journey that is not faint of heart. You can easily drop 15k.
If you want a car that runs and drives, look in the classifieds, you can often find motors in various configurations that you may find suitable.
If you have the space, tools and aptitude, you may want to rebuild it yourself.
Too many projects get stalled when the technical issues pop up and the cash runs out. Put together a budget for the project and plan accordingly. You will be in a better position to deal with surprises.
Best wishes