Joined: Jan 2008
Posts: 23,639
Likes: 1,106
From: Mans of NC & SW UT Desert
Bikes: 86 Katakura Silk, 87 Prologue X2, 88 Cimarron LE, 1975 Sekai 4000 Professional, 73 Paramount, plus more
Not so sure it is a 78, but it might be. Best bet is to check the date codes on major components, starting with the crankset. I had a similar crankset on a 1977 bike, so you could be spot on with your 1978 estimate.