NEVER use wirewounds for an RF load. at RF frequencies, they are inductors and are a much higher impedance than their resistance, and for all intents and purposes might as well be an open circuit.
. BTW, to get 1 watt out of the 2N3866, you need 100mW input, as the transistor's power gain is only 10db. 1 watt is +30dbm (db referenced to 1 milliwatt). subtract the power gain from the desired level, and you get +20dbm, which is 100mw. so to get to 1 watt out from 10mw, you need another stage with a power gain of 10db.
below is the 400Mhz test circuit for the 2N3866. if you DOUBLE both the cap values AND the inductor values, it will work at 100Mhz. if you build an amp, even for 100Mhz, you will need to keep all component leads VERY short. "ugly construction" on a ground plane would probably be the best construction method. with 1W of RF out, the transistor dissipates 5V of heat, so the transistor may have to be heat sinked, which may not be easy, because the collector is the output element, and heat sinking will introduce a lot of capacitance to ground. as for output filtering, use a good 2 or 3 stage PI filter to eliminate harmonics. harmonics will not show up in the FM band, but at around 200, 300, 400, and 500Mhz (assuming a 100Mhz output). 200 and 300Mhz harmonics will be the strongest, so your PI filter should have a cutoff frequency of 120-150Mhz.