A warm welcome to the forum Dennis
with regard getting a donor or buying individual parts........a lot depends on whether you have the space to strip a donor, this is the cheaper route as buying individual parts can cost a little more but has its advantages that you end up working with "just" the parts you need etc & takes up less time, tho having a full donor means you,ll have all the donor parts all at the same time.
Have fun with your build, if you get stuck, this forum is full of very helpful knowledgeable Roadster builders who are always willing to help a fellow builder, have a good read of the various sections of the forum & if you have a question you can,t find an answer to then post up your question & you,ll receive helpful info from the forum members I,m sure.
cheers
andy