Over the years I've learned that any timeline I come up with should be multiplied by at least 2, and if this is planned for only part-time work a multiplication factor of 3-4 might be more accurate. Unfortunately these personal projects are just that... on personal time and have to take a back seat to professional responsibilities and anything else that happens to come up.
If you have a full time job besides this and plan on doing a unique build that involves a lot of custom design like my build I would allocate at least a year to complete. Now this assumes that you're willing to dedicate almost every weekend to the build. If you want to be more realistic (as I've learned), multiply by 2-3 and you get a timeline that more accurately accounts for having a personal life, and just taking care of everything else that comes up.
Before you start a conversion, make sure you have an accurate estimate of time and resources that you'll need to put into this. I just hate to see people abandon projects half way through because it ended up taking more time and resources than they were able to dedicate.
Its a very rewarding experience, but just make sure you prepare and commit to realistic estimates before you jump in head first.