Note: Back then the bike was advertised as a 900cc, however this was a marketing technique used by Harley-Davidson when they rounded up the cc from 883 to 900, making the engine appear bigger than it really was. The bike above is the rare Boat-tail model. One of Peter's many bikes.
The 1970 Cycle Guide Magazine article gives evidence of what is required....
"A Harley-Davidson CH gas tank replaced the standard turtle tank. The front wheel was replaced with a 21" aluminum rim carrying a 3.00 x 21 ribbed Avon Speedmaster tire. The front fender was changed to a chromeplated, bobbed piece and the headlight nacelle, or housing, was removed and a chrome sports light replaced it. The oil tank and rear shock springs were chrome plated. A kickstart was added although the Sportster carries an electric starter. The seat was replaced with a custom leather unit and a short chrome hand-hold was mounted behind the passenger seat. (Folklore has it that the sissy bar was cobbled from a Schwinn banana seat bicycle - ed.) The chain guard cover and the voltage regulator cover were chrome plated. The rear fender was bobbed 5 inches and the tail light replaced with an old style English light. The motorcycle was repainted with a specially mixed formula which is called from this point on, Bronson Red. The final touch was the addition of the Bronson "Eye" insignia to the gas tank."
The 883's pictured here below are a 1970 XLH and 1969, a kick starter was added later. A 1970 has a slightly different front fork because of the way the front fender mounts, but can be adapted by welding tabs on the forks for the Bronson front fender. A vintage XLH is hard to find now-a-days. Once you have your bike, move on to another step.