Swapping newer Hemi into older Dart

It sounds like you are considering using a 3rd gen Hemi engine from a 2003 Ram 2500 in a swap project, and are wondering whether this is a good idea given the high mileage of the engine and your budget constraints.
In general, using a high-mileage engine in a swap project can be somewhat risky, as it is difficult to determine the overall condition of the engine without performing a thorough inspection and diagnostic tests. If the engine has not been well-maintained or has experienced significant wear and tear, it may be more prone to issues or failures. This could result in additional costs for repairs or replacements, which could exceed your budget for the project.
One option to consider is to look for a lower mileage engine that has been well-maintained and is in good condition. This may be more expensive upfront, but it could save you money in the long run by reducing the risk of costly repairs or replacements.
Alternatively, you could consider rebuilding the high-mileage engine that you have. This would involve disassembling the engine, replacing any worn or damaged components, and reassembling it to factory specifications. This can be a time-consuming and labor-intensive process, but it can be a more cost-effective way to get a good-quality engine for your swap project.
As for the feasibility of using a 3rd gen Hemi engine in a 3rd gen Dart coupe, it is possible to perform this type of swap, but it will require a significant amount of work and modification. You will need to fabricate custom motor mounts, modify the firewall and floorpan to accommodate the engine, and modify the wiring and plumbing to make everything work together. This is a complex and challenging project that will require a good understanding of automotive mechanics and a high level of skill and expertise. If you are not confident in your ability to perform this type of work, it is a good idea to consult with a mechanic or a fabricator for assistance.