I can't comment on "Mustang parts", but I have bought several electric guitars and some tactical rifle parts (slings/mounts) and I have been happy with all my purchases. Be warned however as it applies to shipping times. I ordered/bought an electric guitar shortly after Christmas, and it arrived eight days later!
But some smaller items I have bought have taken a month or slightly longer to show up at my door. But I assumed that going in.
I've purchased carbon fibre overlays (what Dyna Performance sells) from Aliexpress, TPIC is the seller. Stuff arrived in about 2 weeks and seems to be the same stuff that Dyna sells. Love the pieces I got and will definitely order some more!
Aliexpress supposedly guarantees the items you buy. You have to confirm to them that you recieved the proper item and only then do they release the payment to the seller. I haven't had to use it yet, but if you dispute the sale you can get refunded.
I have heard of bad sellers on there, so just look at the seller ratings before buying. And also be aware that most items come in on a slow boat from China, so plan on at least a few weeks for delivery.
I'm also wondering that especially because the GT350 Conversion kit which I saw in person recently and it looked amazing. It's 3100$ though for everything bumper, fenders, hood and rear spoiler.
But my brother is ordering tons of shit from AliExpress and never we had any problems besides delivery times. But there is plenty of time till summer
If quality and fit/finish matter to you don't buy anything from aliexpress. I've bought various stuff from there ranging from electronics to clothes to motorcycle luggage and the quality is always bad.
I've bought a bunch of little things from Ali, and they're mostly worth what I paid. My one big-ticket item was the CF spoiler, which had a couple of rough spots on the corners, but the body shop that I took it to for painting managed to fix those spots with fiberglass and now you'd never know it was less than perfect.