G1's were FN produced and components were quality. Imbel receiver is solid and were licensed by FN. IIRC the G1 kits came out of Turkey prior to refurbishment so, I'd check out the bbl condition closely as some were rode hard.
Agree with posted above regarding builder questions. Century was a nightmare on build quality. I bought a Century assembled L1A1(Brit pattern FAL) on and Argentine receiver year ago and upon disassembly, I found that they have destroyed the wrench flats for tightening the bbl. The angry beavers peeled metal away and the headspace was off. I lucked into another bbl and had Glen Riddle at Magnum Gunsmithing rebuilt my rifle into something I'm proud to have in the collection.
Few oddball G1 issues:
The FH is held on by a lug on the bbl, there aren't any threads.
Sheet metal handguards get hot
Bipods are heavy and shift POI in these rifles