You might want to consider a girder fork instead of a springer fork. A girder looks kind of the same, but pivots at the head instead of having links at the bottom, and moves as a unit. At the extreme rake like on the "Capt. America style" bike you pictured, and with the long front extension, springer forks lose some effectiveness and the long levers on the leading links can give some front wheel wobble, as the two spring rods get out of sync. A fork like that can be pretty rigid, even totally rigid and still give some spring. It's so long, it will flex.
Those things will make a man out of you at low speed, especially with the short straight bars pictured. You might have to put considerable force into the bars to keep the front wheel pointed where you want. Ape hangers can help, or wider bars, anything to increase the torque you are putting in with a given amount of force.
My buddy has a long girder fork, hard tailed XLCH. I tell him it's the safest kind of bike he could possibly own, because it spends 98% of the time in the garage.
Another issue that comes up with a long fork, and the tiny hub like in the "Capt. America bike" picture, is front brake effectiveness. My buddy's bike has a teeny little 4" drum, which looks to be about what is pictured. With the small size of the drum, and looooong cable (and proportional compression), he doesn't get much braking action at all out of his front brake. 60 mph to zero stopping distance on the order of 100 feet. It is better than what he had before though, ... which was rear brake only.
Is that a plunger suspension on the rear of the "Capt. America bike"? If so, can you post any detail shots?