Upgrading my front suspension in my 1965 Dodge Dart

Oh boy.

Unfortunately Magnumforce has a pretty poor history, with previous failures and not the best reputation for customer service. There are other coil over conversions available from manufacturers with a much better track record and customer service reputation, like the HDK from @HemiDenny or the RMS from Reilly Motorsports. Both “bolt in” in place of the original suspension.

And to be fair, a lot of the factory K frames had fairly poor welds straight from the factory. Welding them up and reinforcing them is a pretty common thing to do, and can be done for much less than the cost of a full coil over conversion.

There are a lot of options out there to deal with the issues you described, including full coil over conversions, but I would have to say of all of them Magnumforce is probably the least popular option.