The biggest barriers? That one's easy, I can sum up my experience in that regards in three simple words; "garbage reproduction parts."
Well said Eric. I have sympathy for anyone trying to put together a nice car with those crap parts. It's difficult enough to build a sweet car with original parts. At least it was for me...
I was fortunate when building my 67, as it was a very low mile car with almost all original parts. I also collected a stash of nice used & NOS parts for the better part of 10 years while waiting to restore it. Most folks today aren't as lucky. Prices of good used & NOS parts have inflated faster than the cars have!
Luckily for me, the parts that weren't usable on my Chevelle were some of the better resto pieces available. Interior trim, hoses, emblems, & weatherstripping are very comparable to the originals. In some cases, some parts are nicer than the orignals, e.g. Sunvisor supports, & vent window handles.
I don't envy anyone who needs sheet metal, nice original or NOS exterior moldings, nevermind a set of bucket seats. :sad:
My next car will be bought finished, as it's cheaper than building one. IMHO, there is no way to build a NICE one from scratch for less than $45k, unless you are a bodyman/painter & have a stash of GOOD parts to assemble it with.