The oscillator and buffer amplifier, and Filter 2 can also be built on perfboard if frequency stability is not critical. If you only have double-sided board available you'll have to etch away one side. Otherwise, stray capacitance between the two copper surfaces will make the oscillator unstable. Leave some space on the board around crystal Y1. With some crystals small changes in the values of C3 or C4 might be needed so that you can set the frequency to exactly 4 MHz with the trimmer.
Some extra room makes it easier to swap out capacitors.
The 780 ohm R1 resistor in the emitter lead of Q4 is not a standard value but is instead made up with 100 ohm and 680 ohm resistors in series. This will give about 0.58 to 0.64 volts RMS when measured with an RF probe. Any similar material could be used for the mounting plate. The entire converter should be housed in a shielded metal cabinet with suitable RF connectors to prevent strong signals in the 4 MHz band from causing interference. This will minimize capacitive coupling of the strong LO signal directly into the converter input, and prevent degradation of the converter dynamic range.